diff --git a/dom/plugins/PluginInstanceChild.cpp b/dom/plugins/PluginInstanceChild.cpp
index 3ac521ffb148..9b3da065b1ba 100644
--- a/dom/plugins/PluginInstanceChild.cpp
+++ b/dom/plugins/PluginInstanceChild.cpp
@@ -1493,8 +1493,13 @@ PluginInstanceChild::AnswerUpdateWindow()
     PR_LOG(gPluginLog, PR_LOG_DEBUG, ("%s", FULLFUNCTION));
 
 #if defined(OS_WIN)
-    if (mPluginWindowHWND)
-      UpdateWindow(mPluginWindowHWND);
+    if (mPluginWindowHWND) {
+        RECT rect;
+        if (GetUpdateRect(GetParent(mPluginWindowHWND), &rect, FALSE)) {
+            ::InvalidateRect(mPluginWindowHWND, &rect, FALSE); 
+        }
+        UpdateWindow(mPluginWindowHWND);
+    }
     return true;
 #else
     NS_NOTREACHED("PluginInstanceChild::AnswerUpdateWindow not implemented!");