diff --git a/reactos/dll/directx/ddraw/Ddraw/ddraw_setcooperativelevel.c b/reactos/dll/directx/ddraw/Ddraw/ddraw_setcooperativelevel.c
index 43808d2ea9d..1a2d3353e27 100644
--- a/reactos/dll/directx/ddraw/Ddraw/ddraw_setcooperativelevel.c
+++ b/reactos/dll/directx/ddraw/Ddraw/ddraw_setcooperativelevel.c
@@ -33,7 +33,7 @@ Main_DirectDraw_SetCooperativeLevel (LPDIRECTDRAW7 iface, HWND hwnd, DWORD coopl
     }
 #endif
 
-	if(hwnd && IsWindow(hwnd))
+	if(hwnd && !IsWindow(hwnd))
 		return DDERR_INVALIDPARAMS;
 
     /* Tests suggest that we need one of them: */