--- a/modules/plugin/base/src/nsPluginNativeWindowWin.cpp
+++ b/modules/plugin/base/src/nsPluginNativeWindowWin.cpp
@@ -544,17 +544,20 @@ nsresult nsPluginNativeWindowWin::Subcla
   if (PluginWndProc == currentWndProc)
     return NS_OK;
 
   LONG style = GetWindowLongPtr(hWnd, GWL_STYLE);
 #ifdef MOZ_IPC
   // Out of process plugins must not have the WS_CLIPCHILDREN style set on their
   // parent windows or else synchronous paints (via UpdateWindow() and others)
   // will cause deadlocks.
-  style &= ~WS_CLIPCHILDREN;
+  if (::GetPropW(hWnd, L"PluginInstanceParentProperty"))
+    style &= ~WS_CLIPCHILDREN;
+  else
+    style |= WS_CLIPCHILDREN;
 #else
   style |= WS_CLIPCHILDREN;
 #endif
   SetWindowLongPtr(hWnd, GWL_STYLE, style);
 
   mPluginWinProc = SubclassWindow(hWnd, (LONG_PTR)PluginWndProc);
   if (!mPluginWinProc)
     return NS_ERROR_FAILURE;