--- a/widget/windows/nsWindow.cpp
+++ b/widget/windows/nsWindow.cpp
@@ -3763,16 +3763,24 @@ bool nsWindow::DispatchMouseEvent(uint32
   bool result = false;
 
   UserActivity();
 
   if (!mWidgetListener) {
     return result;
   }
 
+  if (WinUtils::GetIsMouseFromTouch(aEventType) && mTouchWindow) {
+    // If mTouchWindow is true, then we must have APZ enabled and be
+    // feeding it raw touch events. In that case we don't need to
+    // send touch-generated mouse events to content.
+    MOZ_ASSERT(mAPZC);
+    return result;
+  }
+
   switch (aEventType) {
     case NS_MOUSE_BUTTON_DOWN:
       CaptureMouse(true);
       break;
 
     // NS_MOUSE_MOVE and NS_MOUSE_EXIT are here because we need to make sure capture flag
     // isn't left on after a drag where we wouldn't see a button up message (see bug 324131).
     case NS_MOUSE_BUTTON_UP:
@@ -3800,20 +3808,19 @@ bool nsWindow::DispatchMouseEvent(uint32
   } else {
     InitEvent(event, &eventPoint);
   }
 
   ModifierKeyState modifierKeyState;
   modifierKeyState.InitInputEvent(event);
   event.button    = aButton;
   event.inputSource = aInputSource;
-  // Convert Mouse events generated by pen device or if mouse not generated from touch
-  event.convertToPointer =
-    aInputSource == nsIDOMMouseEvent::MOZ_SOURCE_PEN ||
-    !(WinUtils::GetIsMouseFromTouch(aEventType) && mTouchWindow);
+  // If we get here the mouse events must be from non-touch sources, so
+  // convert it to pointer events as well
+  event.convertToPointer = true;
 
   nsIntPoint mpScreen = eventPoint + WidgetToScreenOffsetUntyped();
 
   // Suppress mouse moves caused by widget creation
   if (aEventType == NS_MOUSE_MOVE) 
   {
     if ((sLastMouseMovePoint.x == mpScreen.x) && (sLastMouseMovePoint.y == mpScreen.y))
       return result;