diff --git a/frontend/vendor/main.externs.js b/frontend/vendor/main.externs.js
index e44882577..75d7b0a26 100644
--- a/frontend/vendor/main.externs.js
+++ b/frontend/vendor/main.externs.js
@@ -1,4 +1,5 @@
 var TopLevel = {
+  "isDragging": function() {},
   "offsetX": function() {},
   "offsetY": function() {},
   "nativeEvent": function() {},