diff --git a/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py b/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py
index 37b6989add..a947114595 100644
--- a/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py
+++ b/plugins/VersionUpgrade/VersionUpgrade21to22/MachineInstance.py
@@ -1,15 +1,16 @@
-# Copyright (c) 2016 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
-import UM.VersionUpgrade #To indicate that a file is of incorrect format.
-import UM.VersionUpgradeManager #To schedule more files to be upgraded.
-from UM.Resources import Resources #To get the config storage path.
-
 import configparser #To read config files.
 import io #To write config files to strings as if they were files.
 import os.path #To get the path to write new user profiles to.
+from typing import List, Optional, Tuple
 import urllib #To serialise the user container file name properly.
 
+import UM.VersionUpgrade #To indicate that a file is of incorrect format.
+import UM.VersionUpgradeManager #To schedule more files to be upgraded.
+from UM.Resources import Resources #To get the config storage path.
+
 ##  Creates a new machine instance instance by parsing a serialised machine
 #   instance in version 1 of the file format.
 #
@@ -18,7 +19,7 @@ import urllib #To serialise the user container file name properly.
 #   extension.
 #   \return A machine instance instance, or None if the file format is
 #   incorrect.
-def importFrom(serialised, filename):
+def importFrom(serialised: str, filename: str) -> Optional["MachineInstance"]:
     try:
         return MachineInstance(serialised, filename)
     except (configparser.Error, UM.VersionUpgrade.FormatException, UM.VersionUpgrade.InvalidVersionException):
@@ -32,7 +33,7 @@ class MachineInstance:
     #   \param serialised A string with the contents of a machine instance file,
     #   without extension.
     #   \param filename The supposed file name of this machine instance.
-    def __init__(self, serialised, filename):
+    def __init__(self, serialised: str, filename: str) -> str:
         self._filename = filename
 
         config = configparser.ConfigParser(interpolation = None)
@@ -67,7 +68,7 @@ class MachineInstance:
     #
     #   \return A tuple containing the new filename and a serialised form of
     #   this machine instance, serialised in version 2 of the file format.
-    def export(self):
+    def export(self) -> Tuple[List[str], List[str]]:
         config = configparser.ConfigParser(interpolation = None) # Build a config file in the form of version 2.
 
         config.add_section("general")
diff --git a/plugins/VersionUpgrade/VersionUpgrade21to22/Preferences.py b/plugins/VersionUpgrade/VersionUpgrade21to22/Preferences.py
index 842499da86..51e4b617e8 100644
--- a/plugins/VersionUpgrade/VersionUpgrade21to22/Preferences.py
+++ b/plugins/VersionUpgrade/VersionUpgrade21to22/Preferences.py
@@ -1,8 +1,9 @@
-# Copyright (c) 2016 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import configparser #To read config files.
 import io #To output config files to string.
+from typing import List, Optional, Tuple
 
 import UM.VersionUpgrade #To indicate that a file is of the wrong format.
 
@@ -14,7 +15,7 @@ import UM.VersionUpgrade #To indicate that a file is of the wrong format.
 #   extension.
 #   \return A representation of those preferences, or None if the file format is
 #   incorrect.
-def importFrom(serialised, filename):
+def importFrom(serialised: str, filename: str) -> Optional["Preferences"]:
     try:
         return Preferences(serialised, filename)
     except (configparser.Error, UM.VersionUpgrade.FormatException, UM.VersionUpgrade.InvalidVersionException):
@@ -28,7 +29,7 @@ class Preferences:
     #   \param serialised A serialised version 2 preferences file.
     #   \param filename The supposed filename of the preferences file, without
     #   extension.
-    def __init__(self, serialised, filename):
+    def __init__(self, serialised: str, filename: str) -> None:
         self._filename = filename
 
         self._config = configparser.ConfigParser(interpolation = None)
@@ -50,7 +51,7 @@ class Preferences:
     #
     #   \return A tuple containing the new filename and a serialised version of
     #   a preferences file in version 3.
-    def export(self):
+    def export(self) -> Tuple[List[str], List[str]]:
         #Reset the cura/categories_expanded property since it works differently now.
         if self._config.has_section("cura") and self._config.has_option("cura", "categories_expanded"):
             self._config.remove_option("cura", "categories_expanded")
diff --git a/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py b/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py
index 161edcb67c..af9635d384 100644
--- a/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py
+++ b/plugins/VersionUpgrade/VersionUpgrade21to22/Profile.py
@@ -1,10 +1,9 @@
-# Copyright (c) 2016 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import configparser #To read config files.
 import io #To write config files to strings as if they were files.
-from typing import Dict
-from typing import List
+from typing import Dict, List, Optional, Tuple
 
 import UM.VersionUpgrade
 from UM.Logger import Logger
@@ -15,7 +14,7 @@ from UM.Logger import Logger
 #   \param serialised The serialised form of a profile in version 1.
 #   \param filename The supposed filename of the profile, without extension.
 #   \return A profile instance, or None if the file format is incorrect.
-def importFrom(serialised, filename):
+def importFrom(serialised: str, filename: str) -> Optional["Profile"]:
     try:
         return Profile(serialised, filename)
     except (configparser.Error, UM.VersionUpgrade.FormatException, UM.VersionUpgrade.InvalidVersionException):
@@ -77,11 +76,11 @@ class Profile:
     #
     #   \return A tuple containing the new filename and a serialised form of
     #   this profile, serialised in version 2 of the file format.
-    def export(self):
+    def export(self) -> Optional[Tuple[List[str], List[str]]]:
         import VersionUpgrade21to22 # Import here to prevent circular dependencies.
 
         if self._name == "Current settings":
-            return None, None #Can't upgrade these, because the new current profile needs to specify the definition ID and the old file only had the machine instance, not the definition.
+            return None #Can't upgrade these, because the new current profile needs to specify the definition ID and the old file only had the machine instance, not the definition.
 
         config = configparser.ConfigParser(interpolation = None)
 
diff --git a/plugins/VersionUpgrade/VersionUpgrade21to22/VersionUpgrade21to22.py b/plugins/VersionUpgrade/VersionUpgrade21to22/VersionUpgrade21to22.py
index d8036491bf..89c847e606 100644
--- a/plugins/VersionUpgrade/VersionUpgrade21to22/VersionUpgrade21to22.py
+++ b/plugins/VersionUpgrade/VersionUpgrade21to22/VersionUpgrade21to22.py
@@ -1,7 +1,8 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import configparser #To get version numbers from config files.
+from typing import Dict, Iterable, List, Optional, Set, Tuple
 
 from UM.VersionUpgrade import VersionUpgrade # Superclass of the plugin.
 
@@ -30,7 +31,7 @@ _machines_with_machine_quality = {
         "materials": { "generic_abs", "generic_cpe", "generic_pla", "generic_pva", "generic_cpe_plus", "generic_nylon", "generic_pc", "generic_tpu" },
         "variants": { "0.25 mm", "0.4 mm", "0.6 mm", "0.8 mm" }
     }
-}
+} # type: Dict[str, Dict[str, Set[str]]]
 
 ##  How to translate material names from the old version to the new.
 _material_translations = {
@@ -41,7 +42,7 @@ _material_translations = {
     "Nylon": "generic_nylon",
     "PC": "generic_pc",
     "TPU": "generic_tpu",
-}
+} # type: Dict[str, str]
 
 ##  How to translate material names for in the profile names.
 _material_translations_profiles = {
@@ -52,17 +53,17 @@ _material_translations_profiles = {
     "Nylon": "nylon",
     "PC": "pc",
     "TPU": "tpu",
-}
+} # type: Dict[str, str]
 
 ##  How to translate printer names from the old version to the new.
 _printer_translations = {
     "ultimaker2plus": "ultimaker2_plus"
-}
+} # type: Dict[str, str]
 
 _printer_translations_profiles = {
     "ultimaker2plus": "um2p", #Does NOT get included in PLA profiles!
     "ultimaker2_extended_plus": "um2ep" #Has no profiles for CPE+, Nylon, PC and TPU!
-}
+} # type: Dict[str, str]
 
 ##  How to translate profile names from the old version to the new.
 #
@@ -116,13 +117,13 @@ _profile_translations = {
     "tpu_0.25_high": "um2p_tpu_0.25_high",
     "tpu_0.4_normal": "um2p_tpu_0.4_normal",
     "tpu_0.6_fast": "um2p_tpu_0.6_fast"
-}
+} # type: Dict[str, str]
 
 ##  Settings that are no longer in the new version.
 _removed_settings = {
     "fill_perimeter_gaps",
     "support_area_smoothing"
-}
+} # type: Set[str]
 
 ##  How to translate setting names from the old version to the new.
 _setting_name_translations = {
@@ -142,7 +143,7 @@ _setting_name_translations = {
     "support_roof_line_distance": "support_interface_line_distance",
     "support_roof_line_width": "support_interface_line_width",
     "support_roof_pattern": "support_interface_pattern"
-}
+} # type: Dict[str, str]
 
 ##  Custom profiles become quality_changes. This dictates which quality to base
 #   the quality_changes profile on.
@@ -190,7 +191,7 @@ _quality_fallbacks = {
             #No TPU.
         }
     }
-}
+} # type: Dict[str, Dict[str, Dict[str, str]]]
 
 ##  How to translate variants of specific machines from the old version to the
 #   new.
@@ -207,7 +208,7 @@ _variant_translations = {
         "0.6 mm": "ultimaker2_extended_plus_0.6",
         "0.8 mm": "ultimaker2_extended_plus_0.8"
     }
-}
+} # type: Dict[str, Dict[str, str]]
 
 ##  How to translate variant names for in the profile names.
 _variant_translations_profiles = {
@@ -215,7 +216,7 @@ _variant_translations_profiles = {
     "0.4 mm": "0.4",
     "0.6 mm": "0.6",
     "0.8 mm": "0.8"
-}
+} # type: Dict[str, str]
 
 ##  Cura 2.2's material profiles use a different naming scheme for variants.
 #
@@ -233,7 +234,7 @@ _variant_translations_materials = {
         "0.6 mm": "ultimaker2_plus_0.6_mm",
         "0.8 mm": "ultimaker2_plus_0.8_mm"
     }
-}
+} # type: Dict[str, Dict[str, str]]
 
 ##  Converts configuration from Cura 2.1's file formats to Cura 2.2's.
 #
@@ -245,8 +246,8 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   number is stored in general/version, so get the data from that key.
     #
     #   \param serialised The contents of a config file.
-    #   \return \type{int} The version number of that config file.
-    def getCfgVersion(self, serialised):
+    #   \return The version number of that config file.
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -263,7 +264,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \param variant The variant ID of the user's configuration in 2.2.
     #   \param material The material ID of the user's configuration in 2.2.
     @staticmethod
-    def getQualityFallback(machine, variant, material):
+    def getQualityFallback(machine: str, variant: str, material: str) -> str:
         if machine not in _quality_fallbacks:
             return "normal"
         if variant not in _quality_fallbacks[machine]:
@@ -277,14 +278,14 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   This is required to test if profiles should be converted to a quality
     #   profile or a quality-changes profile.
     @staticmethod
-    def builtInProfiles():
+    def builtInProfiles() -> Iterable[str]:
         return _profile_translations.keys()
 
     ##  Gets a set of the machines which now have per-material quality profiles.
     #
     #   \return A set of machine identifiers.
     @staticmethod
-    def machinesWithMachineQuality():
+    def machinesWithMachineQuality() -> Dict[str, Dict[str, Set[str]]]:
         return _machines_with_machine_quality
 
     ##  Converts machine instances from format version 1 to version 2.
@@ -295,10 +296,10 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \return A tuple containing the new filename and the serialised machine
     #   instance in version 2, or None if the input was not of the correct
     #   format.
-    def upgradeMachineInstance(self, serialised, filename):
+    def upgradeMachineInstance(self, serialised: str, filename: str) -> Optional[Tuple[List[str], List[str]]]:
         machine_instance = MachineInstance.importFrom(serialised, filename)
         if not machine_instance: #Invalid file format.
-            return filename, None
+            return None
         return machine_instance.export()
 
     ##  Converts preferences from format version 2 to version 3.
@@ -309,10 +310,10 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \return A tuple containing the new filename and the serialised
     #   preferences in version 3, or None if the input was not of the correct
     #   format.
-    def upgradePreferences(self, serialised, filename):
+    def upgradePreferences(self, serialised: str, filename: str) -> Optional[Tuple[List[str], List[str]]]:
         preferences = Preferences.importFrom(serialised, filename)
         if not preferences: #Invalid file format.
-            return filename, None
+            return None
         return preferences.export()
 
     ##  Converts profiles from format version 1 to version 2.
@@ -322,10 +323,10 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   extension.
     #   \return A tuple containing the new filename and the serialised profile
     #   in version 2, or None if the input was not of the correct format.
-    def upgradeProfile(self, serialised, filename):
+    def upgradeProfile(self, serialised: str, filename: str) -> Optional[Tuple[List[str], List[str]]]:
         profile = Profile.importFrom(serialised, filename)
         if not profile: # Invalid file format.
-            return filename, None
+            return None
         return profile.export()
 
     ##  Translates a material name for the change from Cura 2.1 to 2.2.
@@ -333,7 +334,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \param material A material name in Cura 2.1.
     #   \return The name of the corresponding material in Cura 2.2.
     @staticmethod
-    def translateMaterial(material):
+    def translateMaterial(material: str) -> str:
         if material in _material_translations:
             return _material_translations[material]
         return material
@@ -345,7 +346,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \return The name of the corresponding material in the quality profiles
     #   in Cura 2.2.
     @staticmethod
-    def translateMaterialForProfiles(material):
+    def translateMaterialForProfiles(material: str) -> str:
         if material in _material_translations_profiles:
             return _material_translations_profiles[material]
         return material
@@ -356,7 +357,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \param printer A printer name in Cura 2.1.
     #   \return The name of the corresponding printer in Cura 2.2.
     @staticmethod
-    def translatePrinter(printer):
+    def translatePrinter(printer: str) -> str:
         if printer in _printer_translations:
             return _printer_translations[printer]
         return printer #Doesn't need to be translated.
@@ -367,7 +368,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \param printer A printer name in 2.1.
     #   \return The name of the corresponding printer in Cura 2.2.
     @staticmethod
-    def translatePrinterForProfile(printer):
+    def translatePrinterForProfile(printer: str) -> str:
         if printer in _printer_translations_profiles:
             return _printer_translations_profiles[printer]
         return printer
@@ -378,7 +379,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \param profile A profile name in the old version.
     #   \return The corresponding profile name in the new version.
     @staticmethod
-    def translateProfile(profile):
+    def translateProfile(profile: str) -> str:
         if profile in _profile_translations:
             return _profile_translations[profile]
         return profile #Doesn't need to be translated.
@@ -392,7 +393,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \param settings A dictionary of settings (as key-value pairs) to update.
     #   \return The same dictionary.
     @staticmethod
-    def translateSettings(settings):
+    def translateSettings(settings: Dict[str, str]) -> Dict[str, str]:
         new_settings = {}
         for key, value in settings.items():
             if key in _removed_settings:
@@ -414,7 +415,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \param setting The name of a setting in Cura 2.1.
     #   \return The name of the corresponding setting in Cura 2.2.
     @staticmethod
-    def translateSettingName(setting):
+    def translateSettingName(setting: str) -> str:
         if setting in _setting_name_translations:
             return _setting_name_translations[setting]
         return setting #Doesn't need to be translated.
@@ -426,7 +427,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   2.2's naming.
     #   \return The name of the corresponding variant in Cura 2.2.
     @staticmethod
-    def translateVariant(variant, machine):
+    def translateVariant(variant: str, machine: str) -> str:
         if machine in _variant_translations and variant in _variant_translations[machine]:
             return _variant_translations[machine][variant]
         return variant
@@ -440,7 +441,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \return The name of the corresponding variant for in material profiles
     #   in Cura 2.2.
     @staticmethod
-    def translateVariantForMaterials(variant, machine):
+    def translateVariantForMaterials(variant: str, machine: str) -> str:
         if machine in _variant_translations_materials and variant in _variant_translations_materials[machine]:
             return _variant_translations_materials[machine][variant]
         return variant
@@ -452,7 +453,7 @@ class VersionUpgrade21to22(VersionUpgrade):
     #   \return The name of the corresponding variant for in quality profiles in
     #   Cura 2.2.
     @staticmethod
-    def translateVariantForProfiles(variant):
+    def translateVariantForProfiles(variant: str) -> str:
         if variant in _variant_translations_profiles:
             return _variant_translations_profiles[variant]
         return variant
\ No newline at end of file
diff --git a/plugins/VersionUpgrade/VersionUpgrade21to22/__init__.py b/plugins/VersionUpgrade/VersionUpgrade21to22/__init__.py
index 609781ebfe..67530b9d45 100644
--- a/plugins/VersionUpgrade/VersionUpgrade21to22/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade21to22/__init__.py
@@ -1,11 +1,16 @@
-# Copyright (c) 2016 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade21to22
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade21to22.VersionUpgrade21to22()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                         To                         Upgrade function
@@ -33,5 +38,5 @@ def getMetaData():
         }
     }
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }
diff --git a/plugins/VersionUpgrade/VersionUpgrade22to24/VersionUpgrade.py b/plugins/VersionUpgrade/VersionUpgrade22to24/VersionUpgrade.py
index a56f1f807b..48af365877 100644
--- a/plugins/VersionUpgrade/VersionUpgrade22to24/VersionUpgrade.py
+++ b/plugins/VersionUpgrade/VersionUpgrade22to24/VersionUpgrade.py
@@ -1,18 +1,18 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import configparser #To get version numbers from config files.
+import io
 import os
 import os.path
-import io
+from typing import Dict, List, Optional, Tuple
 
 from UM.Resources import Resources
 from UM.VersionUpgrade import VersionUpgrade # Superclass of the plugin.
 import UM.VersionUpgrade
 
 class VersionUpgrade22to24(VersionUpgrade):
-
-    def upgradeMachineInstance(self, serialised, filename):
+    def upgradeMachineInstance(self, serialised: str, filename: str) -> Optional[Tuple[List[str], List[str]]]:
         # All of this is needed to upgrade custom variant machines from old Cura to 2.4 where
         # `definition_changes` instance container has been introduced. Variant files which
         # look like the the handy work of the old machine settings plugin are converted directly
@@ -71,7 +71,7 @@ class VersionUpgrade22to24(VersionUpgrade):
         config.write(output)
         return [filename], [output.getvalue()]
 
-    def __convertVariant(self, variant_path):
+    def __convertVariant(self, variant_path: str) -> str:
         # Copy the variant to the machine_instances/*_settings.inst.cfg
         variant_config = configparser.ConfigParser(interpolation = None)
         with open(variant_path, "r", encoding = "utf-8") as fhandle:
@@ -99,7 +99,7 @@ class VersionUpgrade22to24(VersionUpgrade):
 
         return config_name
 
-    def __getUserVariants(self):
+    def __getUserVariants(self) -> List[Dict[str, str]]:
         resource_path = Resources.getDataStoragePath()
         variants_dir = os.path.join(resource_path, "variants")
 
@@ -113,7 +113,7 @@ class VersionUpgrade22to24(VersionUpgrade):
                     result.append( { "path": entry.path, "name": config.get("general", "name") } )
         return result
 
-    def upgradeExtruderTrain(self, serialised, filename):
+    def upgradeExtruderTrain(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         config = configparser.ConfigParser(interpolation = None)
         config.read_string(serialised) # Read the input string as config file.
         config.set("general", "version", "3")   # Just bump the version number. That is all we need for now.
@@ -122,7 +122,7 @@ class VersionUpgrade22to24(VersionUpgrade):
         config.write(output)
         return [filename], [output.getvalue()]
 
-    def upgradePreferences(self, serialised, filename):
+    def upgradePreferences(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         config = configparser.ConfigParser(interpolation = None)
         config.read_string(serialised)
 
@@ -142,7 +142,7 @@ class VersionUpgrade22to24(VersionUpgrade):
         config.write(output)
         return [filename], [output.getvalue()]
 
-    def upgradeQuality(self, serialised, filename):
+    def upgradeQuality(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         config = configparser.ConfigParser(interpolation = None)
         config.read_string(serialised) # Read the input string as config file.
         config.set("metadata", "type", "quality_changes")   # Update metadata/type to quality_changes
@@ -152,7 +152,7 @@ class VersionUpgrade22to24(VersionUpgrade):
         config.write(output)
         return [filename], [output.getvalue()]
 
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
diff --git a/plugins/VersionUpgrade/VersionUpgrade22to24/__init__.py b/plugins/VersionUpgrade/VersionUpgrade22to24/__init__.py
index 278b660ec1..fe79333544 100644
--- a/plugins/VersionUpgrade/VersionUpgrade22to24/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade22to24/__init__.py
@@ -1,11 +1,16 @@
-# Copyright (c) 2016 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade.VersionUpgrade22to24()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                         To                 Upgrade function
@@ -26,5 +31,5 @@ def getMetaData():
         }
     }
 
-def register(app):
+def register(app: "Application"):
     return { "version_upgrade": upgrade }
diff --git a/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py b/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py
index 6643edb765..5c9b94cca3 100644
--- a/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py
+++ b/plugins/VersionUpgrade/VersionUpgrade25to26/VersionUpgrade25to26.py
@@ -4,6 +4,7 @@
 import configparser #To parse the files we need to upgrade and write the new files.
 import io #To serialise configparser output to a string.
 import os
+from typing import Dict, List, Set, Tuple
 from urllib.parse import quote_plus
 
 from UM.Resources import Resources
@@ -12,19 +13,18 @@ from UM.VersionUpgrade import VersionUpgrade
 _removed_settings = { #Settings that were removed in 2.5.
     "start_layers_at_same_position",
     "sub_div_rad_mult"
-}
+} # type: Set[str]
 
 _split_settings = { #These settings should be copied to all settings it was split into.
     "support_interface_line_distance": {"support_roof_line_distance", "support_bottom_line_distance"}
-}
+} # type: Dict[str, Set[str]]
 
 ##  A collection of functions that convert the configuration of the user in Cura
 #   2.5 to a configuration for Cura 2.6.
 #
 #   All of these methods are essentially stateless.
 class VersionUpgrade25to26(VersionUpgrade):
-
-    def __init__(self):
+    def __init__(self) -> None:
         super().__init__()
         self._current_fdm_printer_count = 2
 
@@ -39,7 +39,7 @@ class VersionUpgrade25to26(VersionUpgrade):
     #   \raises ValueError The format of the version number in the file is
     #   incorrect.
     #   \raises KeyError The format of the file is incorrect.
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -50,7 +50,7 @@ class VersionUpgrade25to26(VersionUpgrade):
     #
     #   \param serialised The serialised form of a preferences file.
     #   \param filename The name of the file to upgrade.
-    def upgradePreferences(self, serialised, filename):
+    def upgradePreferences(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
@@ -86,7 +86,7 @@ class VersionUpgrade25to26(VersionUpgrade):
     #
     #   \param serialised The serialised form of a quality profile.
     #   \param filename The name of the file to upgrade.
-    def upgradeInstanceContainer(self, serialised, filename):
+    def upgradeInstanceContainer(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
@@ -116,7 +116,7 @@ class VersionUpgrade25to26(VersionUpgrade):
     #
     #   \param serialised The serialised form of a quality profile.
     #   \param filename The name of the file to upgrade.
-    def upgradeMachineStack(self, serialised, filename):
+    def upgradeMachineStack(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
@@ -149,7 +149,7 @@ class VersionUpgrade25to26(VersionUpgrade):
         return [filename], [output.getvalue()]
 
     ##  Acquires the next unique extruder stack index number for the Custom FDM Printer.
-    def _acquireNextUniqueCustomFdmPrinterExtruderStackIdIndex(self):
+    def _acquireNextUniqueCustomFdmPrinterExtruderStackIdIndex(self) -> int:
         extruder_stack_dir = os.path.join(Resources.getDataStoragePath(), "extruders")
         file_name_list = os.listdir(extruder_stack_dir)
         file_name_list = [os.path.basename(file_name) for file_name in file_name_list]
@@ -169,7 +169,7 @@ class VersionUpgrade25to26(VersionUpgrade):
 
         return self._current_fdm_printer_count
 
-    def _checkCustomFdmPrinterHasExtruderStack(self, machine_id):
+    def _checkCustomFdmPrinterHasExtruderStack(self, machine_id: str) -> bool:
         # go through all extruders and make sure that this custom FDM printer has extruder stacks.
         extruder_stack_dir = os.path.join(Resources.getDataStoragePath(), "extruders")
         has_extruders = False
@@ -197,7 +197,7 @@ class VersionUpgrade25to26(VersionUpgrade):
 
         return has_extruders
 
-    def _createCustomFdmPrinterExtruderStack(self, machine_id: str, position: int, quality_id: str, material_id: str):
+    def _createCustomFdmPrinterExtruderStack(self, machine_id: str, position: int, quality_id: str, material_id: str) -> None:
         stack_id = "custom_extruder_%s" % (position + 1)
         if self._current_fdm_printer_count > 1:
             stack_id += " #%s" % self._current_fdm_printer_count
@@ -256,7 +256,7 @@ class VersionUpgrade25to26(VersionUpgrade):
 
     ##  Creates a definition changes container which doesn't contain anything for the Custom FDM Printers.
     #   The container ID will be automatically generated according to the given stack name.
-    def _getCustomFdmPrinterDefinitionChanges(self, stack_id: str):
+    def _getCustomFdmPrinterDefinitionChanges(self, stack_id: str) -> configparser.ConfigParser:
         # In 2.5, there is no definition_changes container for the Custom FDM printer, so it should be safe to use the
         # default name unless some one names the printer as something like "Custom FDM Printer_settings".
         definition_changes_id = stack_id + "_settings"
@@ -277,7 +277,7 @@ class VersionUpgrade25to26(VersionUpgrade):
 
     ##  Creates a user settings container which doesn't contain anything for the Custom FDM Printers.
     #   The container ID will be automatically generated according to the given stack name.
-    def _getCustomFdmPrinterUserSettings(self, stack_id: str):
+    def _getCustomFdmPrinterUserSettings(self, stack_id: str) -> configparser.ConfigParser:
         # For the extruder stacks created in the upgrade, also create user_settings containers so the user changes
         # will be saved.
         user_settings_id = stack_id + "_user"
diff --git a/plugins/VersionUpgrade/VersionUpgrade25to26/__init__.py b/plugins/VersionUpgrade/VersionUpgrade25to26/__init__.py
index 67aa73233f..c74b3218b6 100644
--- a/plugins/VersionUpgrade/VersionUpgrade25to26/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade25to26/__init__.py
@@ -1,11 +1,16 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade25to26
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade25to26.VersionUpgrade25to26()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                          To                          Upgrade function
@@ -41,5 +46,5 @@ def getMetaData():
         }
     }
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }
diff --git a/plugins/VersionUpgrade/VersionUpgrade26to27/VersionUpgrade26to27.py b/plugins/VersionUpgrade/VersionUpgrade26to27/VersionUpgrade26to27.py
index dfa436e5bd..96307ca43c 100644
--- a/plugins/VersionUpgrade/VersionUpgrade26to27/VersionUpgrade26to27.py
+++ b/plugins/VersionUpgrade/VersionUpgrade26to27/VersionUpgrade26to27.py
@@ -3,6 +3,7 @@
 
 import configparser #To parse the files we need to upgrade and write the new files.
 import io #To serialise configparser output to a string.
+from typing import Dict, List, Tuple
 
 from UM.VersionUpgrade import VersionUpgrade
 
@@ -61,7 +62,7 @@ _renamed_quality_profiles = {
 
     "um3_bb0.8_TPU_Not_Supported_Quality": "um3_bb0.8_TPU_Fast_print",
     "um3_bb0.8_TPU_Not_Supported_Superdraft_Quality": "um3_bb0.8_TPU_Superdraft_Print",
-}
+} # type: Dict[str, str]
 
 ##  A collection of functions that convert the configuration of the user in Cura
 #   2.6 to a configuration for Cura 2.7.
@@ -79,7 +80,7 @@ class VersionUpgrade26to27(VersionUpgrade):
     #   \raises ValueError The format of the version number in the file is
     #   incorrect.
     #   \raises KeyError The format of the file is incorrect.
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -90,7 +91,7 @@ class VersionUpgrade26to27(VersionUpgrade):
     #
     #   \param serialised The serialised form of a preferences file.
     #   \param filename The name of the file to upgrade.
-    def upgradePreferences(self, serialised, filename):
+    def upgradePreferences(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation=None)
         parser.read_string(serialised)
 
@@ -117,8 +118,8 @@ class VersionUpgrade26to27(VersionUpgrade):
     #
     #   \param serialised The serialised form of a container file.
     #   \param filename The name of the file to upgrade.
-    def upgradeOtherContainer(self, serialised, filename):
-        parser = configparser.ConfigParser(interpolation=None)
+    def upgradeOtherContainer(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
+        parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
         # Update version numbers
@@ -139,7 +140,7 @@ class VersionUpgrade26to27(VersionUpgrade):
     #
     #   \param serialised The serialised form of a container stack.
     #   \param filename The name of the file to upgrade.
-    def upgradeStack(self, serialised, filename):
+    def upgradeStack(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
diff --git a/plugins/VersionUpgrade/VersionUpgrade26to27/__init__.py b/plugins/VersionUpgrade/VersionUpgrade26to27/__init__.py
index 0e26ca8bbf..1952c9ceff 100644
--- a/plugins/VersionUpgrade/VersionUpgrade26to27/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade26to27/__init__.py
@@ -1,11 +1,16 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade26to27
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade26to27.VersionUpgrade26to27()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                          To                             Upgrade function
@@ -59,5 +64,5 @@ def getMetaData():
         }
     }
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }
diff --git a/plugins/VersionUpgrade/VersionUpgrade27to30/VersionUpgrade27to30.py b/plugins/VersionUpgrade/VersionUpgrade27to30/VersionUpgrade27to30.py
index 5a141f1558..c9e9e41f7e 100644
--- a/plugins/VersionUpgrade/VersionUpgrade27to30/VersionUpgrade27to30.py
+++ b/plugins/VersionUpgrade/VersionUpgrade27to30/VersionUpgrade27to30.py
@@ -1,9 +1,10 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import configparser #To parse preference files.
 import io #To serialise the preference files afterwards.
 import os
+from typing import Dict, List, Tuple
 import urllib.parse
 import re
 
@@ -11,7 +12,7 @@ from UM.VersionUpgrade import VersionUpgrade #We're inheriting from this.
 
 _renamed_themes = {
     "cura": "cura-light"
-}
+} # type: Dict[str, str]
 _renamed_i18n = {
     "7s": "en_7S",
     "de": "de_DE",
@@ -28,7 +29,7 @@ _renamed_i18n = {
     "ptbr": "pt_BR",
     "ru": "ru_RU",
     "tr": "tr_TR"
-}
+} # type: Dict[str, str]
 
 
 class VersionUpgrade27to30(VersionUpgrade):
@@ -43,7 +44,7 @@ class VersionUpgrade27to30(VersionUpgrade):
     #   \raises ValueError The format of the version number in the file is
     #   incorrect.
     #   \raises KeyError The format of the file is incorrect.
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -54,8 +55,8 @@ class VersionUpgrade27to30(VersionUpgrade):
     #
     #   \param serialised The serialised form of a preferences file.
     #   \param filename The name of the file to upgrade.
-    def upgradePreferences(self, serialised, filename):
-        parser = configparser.ConfigParser(interpolation=None)
+    def upgradePreferences(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
+        parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
         # Update version numbers
@@ -100,8 +101,8 @@ class VersionUpgrade27to30(VersionUpgrade):
     #
     #   \param serialised The serialised form of the container file.
     #   \param filename The name of the file to upgrade.
-    def upgradeQualityChangesContainer(self, serialised, filename):
-        parser = configparser.ConfigParser(interpolation=None)
+    def upgradeQualityChangesContainer(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
+        parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
         # Update the skin pre-shrink settings:
@@ -156,7 +157,7 @@ class VersionUpgrade27to30(VersionUpgrade):
     #
     #   \param serialised The serialised form of the container file.
     #   \param filename The name of the file to upgrade.
-    def upgradeOtherContainer(self, serialised, filename):
+    def upgradeOtherContainer(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation=None)
         parser.read_string(serialised)
 
@@ -185,7 +186,7 @@ class VersionUpgrade27to30(VersionUpgrade):
     #
     #   \param serialised The serialised form of a container stack.
     #   \param filename The name of the file to upgrade.
-    def upgradeStack(self, serialised, filename):
+    def upgradeStack(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation=None)
         parser.read_string(serialised)
 
diff --git a/plugins/VersionUpgrade/VersionUpgrade27to30/__init__.py b/plugins/VersionUpgrade/VersionUpgrade27to30/__init__.py
index 4da7257b1c..bddc71a1e0 100644
--- a/plugins/VersionUpgrade/VersionUpgrade27to30/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade27to30/__init__.py
@@ -1,11 +1,16 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade27to30
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade27to30.VersionUpgrade27to30()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                    To                       Upgrade function
@@ -51,5 +56,5 @@ def getMetaData():
         }
     }
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }
diff --git a/plugins/VersionUpgrade/VersionUpgrade30to31/VersionUpgrade30to31.py b/plugins/VersionUpgrade/VersionUpgrade30to31/VersionUpgrade30to31.py
index 399eb18b5d..74467d67c6 100644
--- a/plugins/VersionUpgrade/VersionUpgrade30to31/VersionUpgrade30to31.py
+++ b/plugins/VersionUpgrade/VersionUpgrade30to31/VersionUpgrade30to31.py
@@ -1,14 +1,15 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
 import configparser #To parse preference files.
 import io #To serialise the preference files afterwards.
+from typing import Dict, List, Set, Tuple
 
 from UM.VersionUpgrade import VersionUpgrade #We're inheriting from this.
 
 
 # a list of all legacy "Not Supported" quality profiles
-_OLD_NOT_SUPPORTED_PROFILES = [
+_OLD_NOT_SUPPORTED_PROFILES = {
     "um2p_pp_0.25_normal",
     "um2p_tpu_0.8_normal",
     "um3_bb0.4_ABS_Fast_Print",
@@ -42,7 +43,7 @@ _OLD_NOT_SUPPORTED_PROFILES = [
     "um3_bb0.8_PP_Superdraft_Print",
     "um3_bb0.8_TPU_Fast_print",
     "um3_bb0.8_TPU_Superdraft_Print",
-]
+} # type: Set[str]
 
 
 # Some containers have their specific empty containers, those need to be set correctly.
@@ -51,13 +52,13 @@ _EMPTY_CONTAINER_DICT = {
     "2": "empty_quality",
     "3": "empty_material",
     "4": "empty_variant",
-}
+} # type: Dict[str, str]
 
 
 # Renamed definition files
 _RENAMED_DEFINITION_DICT = {
     "jellybox": "imade3d_jellybox",
-}
+} # type: Dict[str, str]
 
 
 class VersionUpgrade30to31(VersionUpgrade):
@@ -72,7 +73,7 @@ class VersionUpgrade30to31(VersionUpgrade):
     #   \raises ValueError The format of the version number in the file is
     #   incorrect.
     #   \raises KeyError The format of the file is incorrect.
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -83,7 +84,7 @@ class VersionUpgrade30to31(VersionUpgrade):
     #
     #   \param serialised The serialised form of a preferences file.
     #   \param filename The name of the file to upgrade.
-    def upgradePreferences(self, serialised, filename):
+    def upgradePreferences(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
@@ -104,7 +105,7 @@ class VersionUpgrade30to31(VersionUpgrade):
     #
     #   \param serialised The serialised form of the container file.
     #   \param filename The name of the file to upgrade.
-    def upgradeInstanceContainer(self, serialised, filename):
+    def upgradeInstanceContainer(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
@@ -129,7 +130,7 @@ class VersionUpgrade30to31(VersionUpgrade):
     #
     #   \param serialised The serialised form of a container stack.
     #   \param filename The name of the file to upgrade.
-    def upgradeStack(self, serialised, filename):
+    def upgradeStack(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
diff --git a/plugins/VersionUpgrade/VersionUpgrade30to31/__init__.py b/plugins/VersionUpgrade/VersionUpgrade30to31/__init__.py
index 7b2c213a31..c5cc851d6a 100644
--- a/plugins/VersionUpgrade/VersionUpgrade30to31/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade30to31/__init__.py
@@ -1,11 +1,16 @@
-# Copyright (c) 2017 Ultimaker B.V.
+# Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade30to31
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade30to31.VersionUpgrade30to31()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                    To                       Upgrade function
@@ -55,5 +60,5 @@ def getMetaData():
         }
     }
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }
diff --git a/plugins/VersionUpgrade/VersionUpgrade32to33/VersionUpgrade32to33.py b/plugins/VersionUpgrade/VersionUpgrade32to33/VersionUpgrade32to33.py
index 18851b82c7..5be58eab3b 100644
--- a/plugins/VersionUpgrade/VersionUpgrade32to33/VersionUpgrade32to33.py
+++ b/plugins/VersionUpgrade/VersionUpgrade32to33/VersionUpgrade32to33.py
@@ -3,6 +3,7 @@
 
 import configparser #To parse preference files.
 import io #To serialise the preference files afterwards.
+from typing import Dict, List, Tuple
 
 from UM.VersionUpgrade import VersionUpgrade #We're inheriting from this.
 
@@ -51,22 +52,22 @@ _EXTRUDER_TO_POSITION = {
     "ultimaker_original_dual_2nd": 1,
     "vertex_k8400_dual_1st": 0,
     "vertex_k8400_dual_2nd": 1
-}
+} # type: Dict[str, int]
 
 _RENAMED_QUALITY_PROFILES = {
     "low": "fast",
     "um2_low": "um2_fast"
-}
+} # type: Dict[str, str]
 
 _RENAMED_QUALITY_TYPES = {
     "low": "fast"
-}
+} # type: Dict[str, str]
 
 ##  Upgrades configurations from the state they were in at version 3.2 to the
 #   state they should be in at version 3.3.
 class VersionUpgrade32to33(VersionUpgrade):
-
     temporary_group_name_counter = 1
+
     ##  Gets the version number from a CFG file in Uranium's 3.2 format.
     #
     #   Since the format may change, this is implemented for the 3.2 format only
@@ -78,7 +79,7 @@ class VersionUpgrade32to33(VersionUpgrade):
     #   \raises ValueError The format of the version number in the file is
     #   incorrect.
     #   \raises KeyError The format of the file is incorrect.
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -89,7 +90,7 @@ class VersionUpgrade32to33(VersionUpgrade):
     #
     #   \param serialised The serialised form of a preferences file.
     #   \param filename The name of the file to upgrade.
-    def upgradePreferences(self, serialised, filename):
+    def upgradePreferences(self, serialised: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
 
@@ -117,7 +118,7 @@ class VersionUpgrade32to33(VersionUpgrade):
     #
     #   \param serialised The serialised form of a container stack.
     #   \param filename The name of the file to upgrade.
-    def upgradeStack(self, serialized, filename):
+    def upgradeStack(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
@@ -141,7 +142,7 @@ class VersionUpgrade32to33(VersionUpgrade):
 
     ##  Upgrades non-quality-changes instance containers to have the new version
     #   number.
-    def upgradeInstanceContainer(self, serialized, filename):
+    def upgradeInstanceContainer(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
@@ -153,7 +154,7 @@ class VersionUpgrade32to33(VersionUpgrade):
         return [filename], [result.getvalue()]
 
     ##  Upgrades a quality changes container to the new format.
-    def upgradeQualityChanges(self, serialized, filename):
+    def upgradeQualityChanges(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
@@ -182,7 +183,7 @@ class VersionUpgrade32to33(VersionUpgrade):
         return [filename], [result.getvalue()]
 
     ##  Upgrades a variant container to the new format.
-    def upgradeVariants(self, serialized, filename):
+    def upgradeVariants(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
diff --git a/plugins/VersionUpgrade/VersionUpgrade32to33/__init__.py b/plugins/VersionUpgrade/VersionUpgrade32to33/__init__.py
index 5073be772d..006b21bc48 100644
--- a/plugins/VersionUpgrade/VersionUpgrade32to33/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade32to33/__init__.py
@@ -1,11 +1,16 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade32to33
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade32to33.VersionUpgrade32to33()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                           To                              Upgrade function
@@ -51,5 +56,5 @@ def getMetaData():
         }
     }
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }
\ No newline at end of file
diff --git a/plugins/VersionUpgrade/VersionUpgrade33to34/VersionUpgrade33to34.py b/plugins/VersionUpgrade/VersionUpgrade33to34/VersionUpgrade33to34.py
index e2241fd195..5077dda8ad 100644
--- a/plugins/VersionUpgrade/VersionUpgrade33to34/VersionUpgrade33to34.py
+++ b/plugins/VersionUpgrade/VersionUpgrade33to34/VersionUpgrade33to34.py
@@ -3,17 +3,17 @@
 
 import configparser #To parse preference files.
 import io #To serialise the preference files afterwards.
+from typing import Dict, List, Tuple
 
 from UM.VersionUpgrade import VersionUpgrade #We're inheriting from this.
 
 _renamed_settings = {
     "infill_hollow": "infill_support_enabled"
-}
+} # type: Dict[str, str]
 
 ##  Upgrades configurations from the state they were in at version 3.3 to the
 #   state they should be in at version 3.4.
 class VersionUpgrade33to34(VersionUpgrade):
-
     ##  Gets the version number from a CFG file in Uranium's 3.3 format.
     #
     #   Since the format may change, this is implemented for the 3.3 format only
@@ -25,7 +25,7 @@ class VersionUpgrade33to34(VersionUpgrade):
     #   \raises ValueError The format of the version number in the file is
     #   incorrect.
     #   \raises KeyError The format of the file is incorrect.
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -34,7 +34,7 @@ class VersionUpgrade33to34(VersionUpgrade):
 
     ##  Upgrades instance containers to have the new version
     #   number.
-    def upgradeInstanceContainer(self, serialized, filename):
+    def upgradeInstanceContainer(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
diff --git a/plugins/VersionUpgrade/VersionUpgrade33to34/__init__.py b/plugins/VersionUpgrade/VersionUpgrade33to34/__init__.py
index 1130c1e9e2..5fd757f843 100644
--- a/plugins/VersionUpgrade/VersionUpgrade33to34/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade33to34/__init__.py
@@ -1,11 +1,16 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade33to34
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade33to34.VersionUpgrade33to34()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                           To                              Upgrade function
@@ -35,5 +40,5 @@ def getMetaData():
     }
 
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }
diff --git a/plugins/VersionUpgrade/VersionUpgrade34to35/VersionUpgrade34to35.py b/plugins/VersionUpgrade/VersionUpgrade34to35/VersionUpgrade34to35.py
index 9d59133036..88cc3ca420 100644
--- a/plugins/VersionUpgrade/VersionUpgrade34to35/VersionUpgrade34to35.py
+++ b/plugins/VersionUpgrade/VersionUpgrade34to35/VersionUpgrade34to35.py
@@ -3,13 +3,14 @@
 
 import configparser
 import io
+from typing import Dict, List, Set, Tuple
 
 from UM.VersionUpgrade import VersionUpgrade
 
-deleted_settings = {"prime_tower_wall_thickness", "dual_pre_wipe", "prime_tower_purge_volume"}
+deleted_settings = {"prime_tower_wall_thickness", "dual_pre_wipe", "prime_tower_purge_volume"} # type: Set[str]
 
-changed_settings = {'retraction_combing': 'noskin'}
-updated_settings = {'retraction_combing': 'infill'}
+changed_settings = {"retraction_combing": "noskin"} # type: Dict[str, str]
+updated_settings = {"retraction_combing": "infill"} # type: Dict[str, str]
 
 _RENAMED_MATERIAL_PROFILES = {
     "dsm_arnitel2045_175_cartesio_0.25_mm": "dsm_arnitel2045_175_cartesio_0.25mm_thermoplastic_extruder",
@@ -57,12 +58,11 @@ _RENAMED_MATERIAL_PROFILES = {
     "ultimaker_pva_cartesio_0.25_mm": "ultimaker_pva_cartesio_0.25mm_thermoplastic_extruder",
     "ultimaker_pva_cartesio_0.4_mm": "ultimaker_pva_cartesio_0.4mm_thermoplastic_extruder",
     "ultimaker_pva_cartesio_0.8_mm": "ultimaker_pva_cartesio_0.8mm_thermoplastic_extruder"
-}
+} # type: Dict[str, str]
 
 ##  Upgrades configurations from the state they were in at version 3.4 to the
 #   state they should be in at version 3.5.
 class VersionUpgrade34to35(VersionUpgrade):
-
     ##  Gets the version number from a CFG file in Uranium's 3.3 format.
     #
     #   Since the format may change, this is implemented for the 3.3 format only
@@ -74,7 +74,7 @@ class VersionUpgrade34to35(VersionUpgrade):
     #   \raises ValueError The format of the version number in the file is
     #   incorrect.
     #   \raises KeyError The format of the file is incorrect.
-    def getCfgVersion(self, serialised):
+    def getCfgVersion(self, serialised: str) -> int:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialised)
         format_version = int(parser.get("general", "version")) #Explicitly give an exception when this fails. That means that the file format is not recognised.
@@ -82,7 +82,7 @@ class VersionUpgrade34to35(VersionUpgrade):
         return format_version * 1000000 + setting_version
 
     ##  Upgrades Preferences to have the new version number.
-    def upgradePreferences(self, serialized, filename):
+    def upgradePreferences(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
@@ -103,7 +103,7 @@ class VersionUpgrade34to35(VersionUpgrade):
         return [filename], [result.getvalue()]
 
     ##  Upgrades stacks to have the new version number.
-    def upgradeStack(self, serialized, filename):
+    def upgradeStack(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
@@ -121,7 +121,7 @@ class VersionUpgrade34to35(VersionUpgrade):
 
     ##  Upgrades instance containers to have the new version
     #   number.
-    def upgradeInstanceContainer(self, serialized, filename):
+    def upgradeInstanceContainer(self, serialized: str, filename: str) -> Tuple[List[str], List[str]]:
         parser = configparser.ConfigParser(interpolation = None)
         parser.read_string(serialized)
 
@@ -147,7 +147,7 @@ class VersionUpgrade34to35(VersionUpgrade):
         parser.write(result)
         return [filename], [result.getvalue()]
 
-    def _resetConcentric3DInfillPattern(self, parser):
+    def _resetConcentric3DInfillPattern(self, parser: configparser.ConfigParser) -> None:
         if "values" not in parser:
             return
 
@@ -161,5 +161,4 @@ class VersionUpgrade34to35(VersionUpgrade):
             if key not in parser["values"]:
                 continue
             if parser["values"][key] == "concentric_3d":
-                del parser["values"][key]
-
+                del parser["values"][key]
\ No newline at end of file
diff --git a/plugins/VersionUpgrade/VersionUpgrade34to35/__init__.py b/plugins/VersionUpgrade/VersionUpgrade34to35/__init__.py
index 2ea74f6194..332bc827b9 100644
--- a/plugins/VersionUpgrade/VersionUpgrade34to35/__init__.py
+++ b/plugins/VersionUpgrade/VersionUpgrade34to35/__init__.py
@@ -1,11 +1,16 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from typing import Any, Dict, TYPE_CHECKING
+
 from . import VersionUpgrade34to35
 
+if TYPE_CHECKING:
+    from UM.Application import Application
+
 upgrade = VersionUpgrade34to35.VersionUpgrade34to35()
 
-def getMetaData():
+def getMetaData() -> Dict[str, Any]:
     return {
         "version_upgrade": {
             # From                           To                              Upgrade function
@@ -52,5 +57,5 @@ def getMetaData():
     }
 
 
-def register(app):
+def register(app: "Application") -> Dict[str, Any]:
     return { "version_upgrade": upgrade }