--- a/widget/windows/nsAppShell.cpp
+++ b/widget/windows/nsAppShell.cpp
@@ -232,17 +232,18 @@ nsAppShell::Init()
     wc.hCursor       = nullptr;
     wc.hbrBackground = (HBRUSH) nullptr;
     wc.lpszMenuName  = (LPCWSTR) nullptr;
     wc.lpszClassName = kWindowClass;
     RegisterClassW(&wc);
   }
 
   mEventWnd = CreateWindowW(kWindowClass, L"nsAppShell:EventWindow",
-                           0, 0, 0, 10, 10, nullptr, nullptr, module, nullptr);
+                            0, 0, 0, 10, 10, HWND_MESSAGE, nullptr, module,
+                            nullptr);
   NS_ENSURE_STATE(mEventWnd);
 
   return nsBaseAppShell::Init();
 }
 
 NS_IMETHODIMP
 nsAppShell::Run(void)
 {