diff --git a/core/renderers/zelos/measurables/top_row.js b/core/renderers/zelos/measurables/top_row.js
index a1817801a..3f4dbafa8 100644
--- a/core/renderers/zelos/measurables/top_row.js
+++ b/core/renderers/zelos/measurables/top_row.js
@@ -49,7 +49,7 @@ Blockly.zelos.TopRow.prototype.endsWithElemSpacer = function() {
  * @override
  */
 Blockly.zelos.TopRow.prototype.hasLeftSquareCorner = function(block) {
-  var hasHat = (block.hat ?
+  const hasHat = (block.hat ?
       block.hat === 'cap' : this.constants_.ADD_START_HATS) &&
       !block.outputConnection && !block.previousConnection;
   return !!block.outputConnection || hasHat;