diff --git a/src/xwidget.c b/src/xwidget.c
index 294e9f8788c..4d1d1169af9 100644
--- a/src/xwidget.c
+++ b/src/xwidget.c
@@ -128,6 +128,9 @@ fails.  */)
   CHECK_FIXNAT (width);
   CHECK_FIXNAT (height);
 
+  if (!EQ (type, Qwebkit))
+    error ("Bad xwidget type");
+
   struct xwidget *xw = allocate_xwidget ();
   Lisp_Object val;
   xw->type = type;