diff --git a/closure/goog/ui/editor/toolbarfactory.js b/closure/goog/ui/editor/toolbarfactory.js
index <HASH>..<HASH> 100644
--- a/closure/goog/ui/editor/toolbarfactory.js
+++ b/closure/goog/ui/editor/toolbarfactory.js
@@ -207,7 +207,7 @@ goog.ui.editor.ToolbarFactory.addFormatOption = function(button, caption, tag) {
   var buttonDom = button.getDomHelper();
   var option = new goog.ui.Option(
       buttonDom.createDom(goog.dom.TagName.DIV, null, caption), tag, buttonDom);
-  option.setId(tag);
+  option.setId(String(tag));
   button.addItem(option);
 };
Prepare for goog.dom.TagName type change.

To improve the type precision of created or accessed elements, the type of goog.dom.TagName members is going to change from string to object instance in cl/<I>. This CL prepares for that and wraps all string-only usages of goog.dom.TagName members into String().

RELNOTES: n/a

-------------
Created by MOE: <URL>