diff --git a/plugins/UM3NetworkPrinting/src/CloudFlowMessage.py b/plugins/UM3NetworkPrinting/src/CloudFlowMessage.py
index 2d7b99b750..4f2f7a71a2 100644
--- a/plugins/UM3NetworkPrinting/src/CloudFlowMessage.py
+++ b/plugins/UM3NetworkPrinting/src/CloudFlowMessage.py
@@ -16,16 +16,19 @@ I18N_CATALOG = i18nCatalog("cura")
 class CloudFlowMessage(Message):
 
     def __init__(self, address: str) -> None:
+
+        image_path = os.path.join(
+            CuraApplication.getInstance().getPluginRegistry().getPluginPath("UM3NetworkPrinting") or "",
+            "resources", "svg", "cloud-flow-start.svg"
+        )
+
         super().__init__(
             text=I18N_CATALOG.i18nc("@info:status",
                                     "Send and monitor print jobs from anywhere using your Ultimaker account."),
             lifetime=0,
             dismissable=True,
             option_state=False,
-            image_source=QUrl.fromLocalFile(os.path.join(
-                    CuraApplication.getInstance().getPluginRegistry().getPluginPath("UM3NetworkPrinting"),
-                    "resources", "svg", "cloud-flow-start.svg"
-            )),
+            image_source=image_path,
             image_caption=I18N_CATALOG.i18nc("@info:status Ultimaker Cloud should not be translated.",
                                              "Connect to Ultimaker Cloud"),
         )
diff --git a/plugins/UM3NetworkPrinting/src/ExportFileJob.py b/plugins/UM3NetworkPrinting/src/ExportFileJob.py
index 7abe1e6d8e..56d15bc835 100644
--- a/plugins/UM3NetworkPrinting/src/ExportFileJob.py
+++ b/plugins/UM3NetworkPrinting/src/ExportFileJob.py
@@ -1,4 +1,4 @@
-from typing import List
+from typing import List, Optional
 
 from UM.FileHandler.FileHandler import FileHandler
 from UM.FileHandler.WriteFileJob import WriteFileJob
@@ -12,7 +12,7 @@ from .MeshFormatHandler import MeshFormatHandler
 ## Job that exports the build plate to the correct file format for the target cluster.
 class ExportFileJob(WriteFileJob):
 
-    def __init__(self, file_handler: FileHandler, nodes: List[SceneNode], firmware_version: str) -> None:
+    def __init__(self, file_handler: Optional[FileHandler], nodes: List[SceneNode], firmware_version: str) -> None:
 
         self._mesh_format_handler = MeshFormatHandler(file_handler, firmware_version)
         if not self._mesh_format_handler.is_valid:
diff --git a/plugins/UM3NetworkPrinting/src/MeshFormatHandler.py b/plugins/UM3NetworkPrinting/src/MeshFormatHandler.py
index 1b13b6c91c..9927bf744e 100644
--- a/plugins/UM3NetworkPrinting/src/MeshFormatHandler.py
+++ b/plugins/UM3NetworkPrinting/src/MeshFormatHandler.py
@@ -32,7 +32,7 @@ class MeshFormatHandler:
     #  \return A dict with the file format details, with the following keys:
     #       {id: str, extension: str, description: str, mime_type: str, mode: int, hide_in_file_dialog: bool}
     @property
-    def preferred_format(self) -> Optional[Dict[str, Union[str, int, bool]]]:
+    def preferred_format(self) -> Dict[str, Union[str, int, bool]]:
         return self._preferred_format
 
     ## Gets the file writer for the given file handler and mime type.
diff --git a/plugins/UM3NetworkPrinting/src/Network/LocalClusterOutputDevice.py b/plugins/UM3NetworkPrinting/src/Network/LocalClusterOutputDevice.py
index f8cf652114..758760ce86 100644
--- a/plugins/UM3NetworkPrinting/src/Network/LocalClusterOutputDevice.py
+++ b/plugins/UM3NetworkPrinting/src/Network/LocalClusterOutputDevice.py
@@ -7,7 +7,6 @@ from PyQt5.QtCore import pyqtSlot, QUrl, pyqtSignal, pyqtProperty
 from PyQt5.QtNetwork import QNetworkReply
 
 from UM.FileHandler.FileHandler import FileHandler
-from UM.FileHandler.WriteFileJob import WriteFileJob
 from UM.Message import Message
 from UM.i18n import i18nCatalog
 from UM.Scene.SceneNode import SceneNode
@@ -130,7 +129,7 @@ class LocalClusterOutputDevice(UltimakerNetworkedPrinterOutputDevice):
 
     ## Handler for when the print job was created locally.
     #  It can now be sent over the network.
-    def _onPrintJobCreated(self, job: WriteFileJob) -> None:
+    def _onPrintJobCreated(self, job: ExportFileJob) -> None:
         self._progress.show()
         parts = [
             self._createFormPart("name=owner", bytes(self._getUserName(), "utf-8"), "text/plain"),
diff --git a/plugins/UM3NetworkPrinting/src/UltimakerNetworkedPrinterOutputDevice.py b/plugins/UM3NetworkPrinting/src/UltimakerNetworkedPrinterOutputDevice.py
index fedead7bce..9e21c0b4de 100644
--- a/plugins/UM3NetworkPrinting/src/UltimakerNetworkedPrinterOutputDevice.py
+++ b/plugins/UM3NetworkPrinting/src/UltimakerNetworkedPrinterOutputDevice.py
@@ -191,7 +191,7 @@ class UltimakerNetworkedPrinterOutputDevice(NetworkedPrinterOutputDevice):
 
         # Keep track of the new printers to show.
         # We create a new list instead of changing the existing one to get the correct order.
-        new_printers = []
+        new_printers = []  # type: List[PrinterOutputModel]
 
         # Check which printers need to be created or updated.
         for index, printer_data in enumerate(remote_printers):