diff --git a/src/NodeRenderer/NodeTypes/wrapNode.js b/src/NodeRenderer/NodeTypes/wrapNode.js
index db012d4a..424c386f 100644
--- a/src/NodeRenderer/NodeTypes/wrapNode.js
+++ b/src/NodeRenderer/NodeTypes/wrapNode.js
@@ -8,7 +8,7 @@ import { isNode } from '../../graph-utils';
 import { Provider } from '../NodeIdContext';
 
 const isInput = e => ['INPUT', 'SELECT', 'TEXTAREA'].includes(e.target.nodeName);
-const isHandle = e => e.target.className.includes('source');
+const isHandle = e => e.target.className && e.target.className.includes('source');
 
 const getHandleBounds = (sel, nodeElement, parentBounds) => {
   const handle = nodeElement.querySelector(sel);