diff --git a/cura/SingleInstance.py b/cura/SingleInstance.py
index b3d4f096fd..8109123df5 100644
--- a/cura/SingleInstance.py
+++ b/cura/SingleInstance.py
@@ -7,12 +7,12 @@ from typing import List, Optional
 
 from PyQt5.QtNetwork import QLocalServer, QLocalSocket
 
-from UM.Application import Application #For typing.
+from UM.Qt.QtApplication import QtApplication #For typing.
 from UM.Logger import Logger
 
 
 class SingleInstance:
-    def __init__(self, application: Application, files_to_open: Optional[List[str]]) -> None:
+    def __init__(self, application: QtApplication, files_to_open: Optional[List[str]]) -> None:
         self._application = application
         self._files_to_open = files_to_open
 
@@ -69,7 +69,7 @@ class SingleInstance:
 
     def _onClientConnected(self) -> None:
         Logger.log("i", "New connection recevied on our single-instance server")
-        connection = None
+        connection = None #type: Optional[QLocalSocket]
         if self._single_instance_server:
             connection = self._single_instance_server.nextPendingConnection()