diff --git a/blocks/text.js b/blocks/text.js
index 641b881eb..9723469e8 100644
--- a/blocks/text.js
+++ b/blocks/text.js
@@ -806,8 +806,7 @@ Blockly.Constants.Text.TEXT_CHARAT_MUTATOR_MIXIN = {
    */
   mutationToDom: function() {
     var container = document.createElement('mutation');
-    var isAt = this.getInput('AT').type == Blockly.INPUT_VALUE;
-    container.setAttribute('at', isAt);
+    container.setAttribute('at', !!this.isAt_);
     return container;
   },
   /**