diff --git a/source/baseObject.py b/source/baseObject.py
index 5819f05f34d..2605ecbdb8e 100755
--- a/source/baseObject.py
+++ b/source/baseObject.py
@@ -140,9 +140,12 @@ def __new__(cls, *args, **kwargs):
 	def _getPropertyViaCache(self,getterMethod=None):
 		if not getterMethod:
 			raise ValueError("getterMethod is None")
+		missing=False
 		try:
 			val=self._propertyCache[getterMethod]
 		except KeyError:
+			missing=True
+		if missing:
 			val=getterMethod(self)
 			self._propertyCache[getterMethod]=val
 		return val
diff --git a/source/comtypesMonkeyPatches.py b/source/comtypesMonkeyPatches.py
index 57d84c06416..c5031c13f6c 100644
--- a/source/comtypesMonkeyPatches.py
+++ b/source/comtypesMonkeyPatches.py
@@ -3,6 +3,47 @@
 #This file is covered by the GNU General Public License.
 #See the file COPYING for more details.
 
+import ctypes
+import _ctypes
+
+# A version of ctypes.WINFUNCTYPE 
+# that produces a WinFunctionType class whose instance will convert COMError into a CallCancelled exception when called as a function.
+old_WINFUNCTYPE=ctypes.WINFUNCTYPE
+def new_WINFUNCTYPE(restype,*argtypes,**kwargs):
+	cls=old_WINFUNCTYPE(restype,*argtypes,**kwargs)
+	class WinFunctionType(cls):
+		# We must manually pull the mandatory class variables from the super class,
+		# as the metaclass of _ctypes.CFuncPtr seems to expect these on the outermost subclass.
+		_argtypes_=cls._argtypes_
+		_restype_=cls._restype_
+		_flags_=cls._flags_
+		def __call__(self,*args,**kwargs):
+			try:
+				return super().__call__(*args,**kwargs)
+			except _ctypes.COMError as e:
+				from core import CallCancelled, RPC_E_CALL_CANCELED
+				if e.args[0]==RPC_E_CALL_CANCELED:
+					# As this is a cancelled COM call,
+					# raise CallCancelled instead of the original COMError.
+					# Also raising from None gives a cleaner traceback,
+					# Hiding the fact we were already in an except block.
+					raise CallCancelled("COM call cancelled") from None
+				# Otherwise, just continue the original COMError exception up the stack.
+				raise
+	return WinFunctionType
+
+# While importing comtypes,
+# Replace WINFUNCTYPE in ctypes with our own version,
+# So that comtypes will use this in all its COM method calls. 
+# As comtypes imports WINFUNCTYPE from ctypes by name,
+# We only need to replace it for the duration of importing comtypes, 
+# as it will then have it for ever.
+ctypes.WINFUNCTYPE=new_WINFUNCTYPE
+try:
+	import comtypes
+finally:
+	ctypes.WINFUNCTYPE=old_WINFUNCTYPE
+
 from logHandler import log
 
 from comtypes import COMError
diff --git a/source/core.py b/source/core.py
index 608fbc1dadc..c0d5a81c62d 100644
--- a/source/core.py
+++ b/source/core.py
@@ -7,16 +7,23 @@
 
 """NVDA core"""
 
-# Do this first to initialise comtypes.client.gen_dir and the comtypes.gen search path.
+RPC_E_CALL_CANCELED = -2147418110
+
+class CallCancelled(Exception):
+	"""Raised when a call is cancelled.
+	"""
+
+# Apply several monky patches to comtypes
+import comtypesMonkeyPatches
+
+# Initialise comtypes.client.gen_dir and the comtypes.gen search path 
+# and Append our comInterfaces directory to the comtypes.gen search path.
+import comtypes
 import comtypes.client
-# Append our comInterfaces directory to the comtypes.gen search path.
 import comtypes.gen
 import comInterfaces
 comtypes.gen.__path__.append(comInterfaces.__path__[0])
 
-#Apply several monky patches to comtypes
-import comtypesMonkeyPatches
-
 import sys
 import winVersion
 import threading
diff --git a/source/logHandler.py b/source/logHandler.py
index 833b444e0f7..74d3003ed71 100755
--- a/source/logHandler.py
+++ b/source/logHandler.py
@@ -167,8 +167,7 @@ def exception(self, msg="", exc_info=True, **kwargs):
 		However, certain exceptions which aren't considered errors (or aren't errors that we can fix) are expected and will therefore be logged at a lower level.
 		"""
 		import comtypes
-		import watchdog
-		from watchdog import RPC_E_CALL_CANCELED
+		from core import CallCancelled, RPC_E_CALL_CANCELED
 		if exc_info is True:
 			exc_info = sys.exc_info()
 
@@ -176,7 +175,7 @@ def exception(self, msg="", exc_info=True, **kwargs):
 		if (
 			(isinstance(exc, WindowsError) and exc.winerror in (ERROR_INVALID_WINDOW_HANDLE, ERROR_TIMEOUT, RPC_S_SERVER_UNAVAILABLE, RPC_S_CALL_FAILED_DNE, EPT_S_NOT_REGISTERED, RPC_E_CALL_CANCELED))
 			or (isinstance(exc, comtypes.COMError) and (exc.hresult in (E_ACCESSDENIED, CO_E_OBJNOTCONNECTED, EVENT_E_ALL_SUBSCRIBERS_FAILED, RPC_E_CALL_REJECTED, RPC_E_CALL_CANCELED, RPC_E_DISCONNECTED) or exc.hresult & 0xFFFF == RPC_S_SERVER_UNAVAILABLE))
-			or isinstance(exc, watchdog.CallCancelled)
+			or isinstance(exc, CallCancelled)
 		):
 			level = self.DEBUGWARNING
 		else:
diff --git a/source/watchdog.py b/source/watchdog.py
index b554799cf8e..bdaa45ca9d2 100644
--- a/source/watchdog.py
+++ b/source/watchdog.py
@@ -19,6 +19,7 @@
 from logHandler import log
 import globalVars
 import core
+from core import CallCancelled
 import NVDAHelper
 
 #settings
@@ -46,10 +47,6 @@
 _watcherThread=None
 _cancelCallEvent = None
 
-class CallCancelled(Exception):
-	"""Raised when a call is cancelled.
-	"""
-
 def alive():
 	"""Inform the watchdog that the core is alive.
 	"""
@@ -196,13 +193,6 @@ def sendMessageCallCanceller(frame, event, arg):
 			raise CallCancelled
 	sys.setprofile(sendMessageCallCanceller)
 
-RPC_E_CALL_CANCELED = -2147418110
-_orig_COMError_init = comtypes.COMError.__init__
-def _COMError_init(self, hresult, text, details):
-	if hresult == RPC_E_CALL_CANCELED:
-		raise CallCancelled
-	_orig_COMError_init(self, hresult, text, details)
-
 def initialize():
 	"""Initialize the watchdog.
 	"""
@@ -218,8 +208,6 @@ def initialize():
 		"cancelCallEvent")
 	# Handle cancelled SendMessage calls.
 	NVDAHelper._setDllFuncPointer(NVDAHelper.localLib, "_notifySendMessageCancelled", _notifySendMessageCancelled)
-	# Monkey patch comtypes to specially handle cancelled COM calls.
-	comtypes.COMError.__init__ = _COMError_init
 	_watcherThread=threading.Thread(target=_watcher)
 	alive()
 	_watcherThread.start()
@@ -232,7 +220,6 @@ def terminate():
 		return
 	isRunning=False
 	oledll.ole32.CoDisableCallCancellation(None)
-	comtypes.COMError.__init__ = _orig_COMError_init
 	# Wake up the watcher so it knows to finish.
 	windll.kernel32.SetWaitableTimer(_coreDeadTimer,
 		ctypes.byref(ctypes.wintypes.LARGE_INTEGER(0)),