diff --git a/core-collapse.html b/core-collapse.html
index 542ae55..494f764 100644
--- a/core-collapse.html
+++ b/core-collapse.html
@@ -13,7 +13,7 @@
 
     <button on-click="{{toggle}}">toggle collapse</button>
     
-    <core-collapse id="collapse"></core-collapse>
+    <core-collapse id="collapse">
       ...
     </core-collapse>