diff --git a/web/debugger.js b/web/debugger.js
index 4f85ccbc3..39c0e829b 100644
--- a/web/debugger.js
+++ b/web/debugger.js
@@ -326,6 +326,8 @@ var Stepper = (function StepperClosure() {
       }
     },
     updateOperatorList: function updateOperatorList(operatorList) {
+      var self = this;
+
       function cboxOnClick() {
         var x = +this.dataset.idx;
         if (this.checked) {