diff --git a/reactos/dll/win32/user32/windows/mdi.c b/reactos/dll/win32/user32/windows/mdi.c
index 05705fc0ab9..ff4d2ed5d2b 100644
--- a/reactos/dll/win32/user32/windows/mdi.c
+++ b/reactos/dll/win32/user32/windows/mdi.c
@@ -161,6 +161,8 @@ HWND* WIN_ListChildren (HWND hWndparent)
       return 0;
     }
 
+  pHwnd[dwCount] = (HWND) 0;
+
   return pHwnd;
 }