diff --git a/widget/src/windows/nsAppShell.cpp b/widget/src/windows/nsAppShell.cpp
index 9b81af7060f..4b69cd5ac44 100644
--- a/widget/src/windows/nsAppShell.cpp
+++ b/widget/src/windows/nsAppShell.cpp
@@ -142,6 +142,7 @@ nsAppShell::ProcessNextNativeEvent(PRBool mayWait)
         ::PeekMessageW(&msg, NULL, 0, 0, PM_REMOVE)) {
       gotMessage = PR_TRUE;
       if (msg.message == WM_QUIT) {
+        ::PostQuitMessage(msg.wParam);
         Exit();
       } else {
         ::TranslateMessage(&msg);