diff --git a/demo/cross-iframe-sand.html b/demo/cross-iframe-sand.html
index 554c024..9c838d6 100644
--- a/demo/cross-iframe-sand.html
+++ b/demo/cross-iframe-sand.html
@@ -59,6 +59,7 @@
       }
 
       iframe {
+        border: unset;
         width: 100%;
         height: 100%;
         /* margins cause infinite resize loops */