diff --git a/xpfe/appshell/src/nsWebShellWindow.cpp b/xpfe/appshell/src/nsWebShellWindow.cpp
index 73e7ffd09141..dc9ae79d562a 100644
--- a/xpfe/appshell/src/nsWebShellWindow.cpp
+++ b/xpfe/appshell/src/nsWebShellWindow.cpp
@@ -1730,7 +1730,14 @@ NS_IMETHODIMP nsWebShellWindow::Destroy()
    }
 #endif
 
+  PR_Lock(mSPTimerLock);
+  if (mSPTimer) {
+    mSPTimer->Cancel();
+    mSPTimer = nsnull;
+    StoreBoundsToXUL(mSPTimerPosition, mSPTimerSize, PR_FALSE);
+  }
+  PR_Unlock(mSPTimerLock);
 
-   return nsXULWindow::Destroy();
+  return nsXULWindow::Destroy();
 }