diff --git a/src/extension-support/block-shape.js b/src/extension-support/block-shape.js
index 9c827ef1a9f..190324b71e2 100644
--- a/src/extension-support/block-shape.js
+++ b/src/extension-support/block-shape.js
@@ -1,3 +1,6 @@
+// Use the constants instead of manually redefining them again
+const ScratchBlocksConstants = require('./scratch-blocks-constants');
+
 /**
  * Types of block shapes
  * @enum {number}
@@ -6,17 +9,17 @@ const BlockShape = {
     /**
      * Output shape: hexagonal (booleans/predicates).
      */
-    HEXAGONAL: 1,
+    HEXAGONAL: ScratchBlocksConstants.OUTPUT_SHAPE_HEXAGONAL,
 
     /**
      * Output shape: rounded (numbers).
      */
-    ROUND: 2,
+    ROUND: ScratchBlocksConstants.OUTPUT_SHAPE_ROUND,
 
     /**
      * Output shape: squared (any/all values; strings).
      */
-    SQUARE: 3,
+    SQUARE: ScratchBlocksConstants.OUTPUT_SHAPE_SQUARE,
 };
 
 module.exports = BlockShape;