diff --git a/cura/GlobalStacksModel.py b/cura/GlobalStacksModel.py
index 289a03d1c4..afee52e769 100644
--- a/cura/GlobalStacksModel.py
+++ b/cura/GlobalStacksModel.py
@@ -1,17 +1,13 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
+from PyQt5.QtCore import pyqtProperty, Qt
+
 from UM.Qt.ListModel import ListModel
-
-from PyQt5.QtCore import pyqtProperty, Qt, pyqtSignal
-
 from UM.Settings.ContainerRegistry import ContainerRegistry
-from UM.Settings.ContainerStack import ContainerStack
 
 from cura.PrinterOutputDevice import ConnectionType
 
-from cura.Settings.GlobalStack import GlobalStack
-
 
 class GlobalStacksModel(ListModel):
     NameRole = Qt.UserRole + 1
@@ -38,6 +34,8 @@ class GlobalStacksModel(ListModel):
 
     ##  Handler for container added/removed events from registry
     def _onContainerChanged(self, container):
+        from cura.Settings.GlobalStack import GlobalStack  # otherwise circular imports
+
         # We only need to update when the added / removed container GlobalStack
         if isinstance(container, GlobalStack):
             self._update()
diff --git a/plugins/FirmwareUpdateChecker/FirmwareUpdateChecker.py b/plugins/FirmwareUpdateChecker/FirmwareUpdateChecker.py
index 13b2e69b63..9c4d498d7e 100644
--- a/plugins/FirmwareUpdateChecker/FirmwareUpdateChecker.py
+++ b/plugins/FirmwareUpdateChecker/FirmwareUpdateChecker.py
@@ -1,7 +1,6 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
 
-import os
 from PyQt5.QtCore import QUrl
 from PyQt5.QtGui import QDesktopServices
 
@@ -13,8 +12,6 @@ from UM.Logger import Logger
 from UM.i18n import i18nCatalog
 from UM.Settings.ContainerRegistry import ContainerRegistry
 
-from cura.Settings.GlobalStack import GlobalStack
-
 from .FirmwareUpdateCheckerJob import FirmwareUpdateCheckerJob
 from .FirmwareUpdateCheckerMessage import FirmwareUpdateCheckerMessage
 
@@ -53,6 +50,7 @@ class FirmwareUpdateChecker(Extension):
 
     def _onContainerAdded(self, container):
         # Only take care when a new GlobalStack was added
+        from cura.Settings.GlobalStack import GlobalStack  # otherwise circular imports
         if isinstance(container, GlobalStack):
             self.checkFirmwareVersion(container, True)
 
diff --git a/plugins/FirmwareUpdateChecker/tests/TestFirmwareUpdateChecker.py b/plugins/FirmwareUpdateChecker/tests/TestFirmwareUpdateChecker.py
index 8cd7083f16..cf61e46d29 100644
--- a/plugins/FirmwareUpdateChecker/tests/TestFirmwareUpdateChecker.py
+++ b/plugins/FirmwareUpdateChecker/tests/TestFirmwareUpdateChecker.py
@@ -7,8 +7,7 @@ from unittest.mock import MagicMock
 
 from UM.Version import Version
 
-from plugins.FirmwareUpdateChecker.FirmwareUpdateCheckerJob import FirmwareUpdateCheckerJob
-from plugins.FirmwareUpdateChecker.FirmwareUpdateCheckerLookup import FirmwareUpdateCheckerLookup
+import FirmwareUpdateChecker
 
 json_data = \
     {
@@ -44,7 +43,7 @@ json_data = \
     ("emmerson", 5),
 ])
 def test_FirmwareUpdateCheckerLookup(id, name):
-    lookup = FirmwareUpdateCheckerLookup(name, json_data.get(name))
+    lookup = FirmwareUpdateChecker.FirmwareUpdateCheckerLookup.FirmwareUpdateCheckerLookup(name, json_data.get(name))
 
     assert lookup.getMachineName() == name
     assert lookup.getMachineId() == id
@@ -58,6 +57,6 @@ def test_FirmwareUpdateCheckerLookup(id, name):
 ])
 def test_FirmwareUpdateCheckerJob_getCurrentVersion(name, version):
     machine_data = json_data.get(name)
-    job = FirmwareUpdateCheckerJob(False, name, machine_data, MagicMock)
+    job = FirmwareUpdateChecker.FirmwareUpdateCheckerJob.FirmwareUpdateCheckerJob(False, name, machine_data, MagicMock)
     job.getUrlResponse = MagicMock(return_value = str(version))  # Pretend like we got a good response from the server
     assert job.getCurrentVersion() == version
diff --git a/plugins/FirmwareUpdateChecker/tests/__init__.py b/plugins/FirmwareUpdateChecker/tests/__init__.py
new file mode 100644
index 0000000000..e69de29bb2