diff --git a/reactos/win32ss/user/user32/windows/window.c b/reactos/win32ss/user/user32/windows/window.c
index 6dc86486660..53ed882e6a2 100644
--- a/reactos/win32ss/user/user32/windows/window.c
+++ b/reactos/win32ss/user/user32/windows/window.c
@@ -1501,7 +1501,9 @@ IsWindow(HWND hWnd)
     PWND Wnd = ValidateHwndNoErr(hWnd);
     if (Wnd != NULL)
     {
-        /* FIXME: If window is being destroyed return FALSE! */
+        if (Wnd->state & WNDS_DESTROYED ||
+            Wnd->state2 & WNDS2_INDESTROY)
+           return FALSE;
         return TRUE;
     }