diff --git a/win32ss/gdi/ntgdi/gdiobj.c b/win32ss/gdi/ntgdi/gdiobj.c
index 07c16e0bcae..00c85f5f9dc 100644
--- a/win32ss/gdi/ntgdi/gdiobj.c
+++ b/win32ss/gdi/ntgdi/gdiobj.c
@@ -1193,6 +1193,12 @@ GreGetObjectOwner(HGDIOBJ hobj)
 {
     ULONG ulIndex, ulOwner;
 
+    if (hobj == NULL)
+    {
+        DPRINT("GreGetObjectOwner: invalid NULL handle\n");
+        return GDI_OBJ_HMGR_RESTRICTED;
+    }
+
     /* Get the handle index */
     ulIndex = GDI_HANDLE_GET_INDEX(hobj);