diff --git a/cura/PickingPass.py b/cura/PickingPass.py
index 2a1abe8f63..40a0aaf949 100644
--- a/cura/PickingPass.py
+++ b/cura/PickingPass.py
@@ -16,7 +16,7 @@ from UM.Scene.Iterator.DepthFirstIterator import DepthFirstIterator
 #
 #   Note that in order to increase precision, the 24 bit depth value is encoded into all three of the R,G & B channels
 class PickingPass(RenderPass):
-    def __init__(self, width: int, height: int):
+    def __init__(self, width: int, height: int) -> None:
         super().__init__("picking", width, height)
 
         self._renderer = Application.getInstance().getRenderer()
diff --git a/cura/PreviewPass.py b/cura/PreviewPass.py
index 436e2719b7..511d379f4b 100644
--- a/cura/PreviewPass.py
+++ b/cura/PreviewPass.py
@@ -33,7 +33,7 @@ def prettier_color(color_list):
 #
 #   This is useful to get a preview image of a scene taken from a different location as the active camera.
 class PreviewPass(RenderPass):
-    def __init__(self, width: int, height: int):
+    def __init__(self, width: int, height: int) -> None:
         super().__init__("preview", width, height, 0)
 
         self._camera = None  # type: Optional[Camera]
diff --git a/cura/PrinterOutputDevice.py b/cura/PrinterOutputDevice.py
index bdac80e61c..ae749ba0dc 100644
--- a/cura/PrinterOutputDevice.py
+++ b/cura/PrinterOutputDevice.py
@@ -224,5 +224,5 @@ class PrinterOutputDevice(QObject, OutputDevice):
     ##  Get the name of device firmware
     #
     #   This name can be used to define device type
-    def getFirmwareName(self) -> str:
+    def getFirmwareName(self) -> Optional[str]:
         return self._firmware_name
\ No newline at end of file
diff --git a/cura/Scene/CuraSceneController.py b/cura/Scene/CuraSceneController.py
index 749c5257a2..4b19271538 100644
--- a/cura/Scene/CuraSceneController.py
+++ b/cura/Scene/CuraSceneController.py
@@ -16,7 +16,7 @@ from UM.Signal import Signal
 class CuraSceneController(QObject):
     activeBuildPlateChanged = Signal()
 
-    def __init__(self, objects_model: ObjectsModel, multi_build_plate_model: MultiBuildPlateModel):
+    def __init__(self, objects_model: ObjectsModel, multi_build_plate_model: MultiBuildPlateModel) -> None:
         super().__init__()
 
         self._objects_model = objects_model