diff --git a/lib/core/Canvas.js b/lib/core/Canvas.js
index b8b3c2128..579f8950e 100644
--- a/lib/core/Canvas.js
+++ b/lib/core/Canvas.js
@@ -73,7 +73,9 @@ function createGroup(parent, cls, childIndex) {
 
   var index = childIndex !== undefined ? childIndex : parent.childNodes.length - 1;
 
-  parent.insertBefore(group, parent.childNodes[index]);
+  // must ensure second argument is node or _null_
+  // cf. https://developer.mozilla.org/en-US/docs/Web/API/Node/insertBefore
+  parent.insertBefore(group, parent.childNodes[index] || null);
 
   return group;
 }