--- a/devtools/server/event-parsers.js
+++ b/devtools/server/event-parsers.js
@@ -264,17 +264,17 @@ var parsers = [
 
       return handlerDO;
     }
   },
 ];
 
 function reactGetListeners(node, boolOnEventFound) {
   function getProps() {
-    for (let key in node) {
+    for (let key of Object.keys(node)) {
       if (key.startsWith("__reactInternalInstance$")) {
         return node[key]._currentElement.props;
       }
     }
     return null;
   }
 
   node = node.wrappedJSObject || node;