diff --git a/www/common/sframe-common-codemirror.js b/www/common/sframe-common-codemirror.js
index c4a18f4e0..96f5fe77d 100644
--- a/www/common/sframe-common-codemirror.js
+++ b/www/common/sframe-common-codemirror.js
@@ -362,7 +362,7 @@ define([
                 editor.setOption('indentWithTabs', useTabs);
                 if (!useTabs) {
                     editor.setOption("extraKeys", {
-                        Tab: function(cm) {
+                        Tab: function() {
                             editor.replaceSelection(Array(units + 1).join(" "));
                         }
                     });