diff --git a/demos/blockfactory/blocks.js b/demos/blockfactory/blocks.js
index 3cb7ca29b..65f75665e 100644
--- a/demos/blockfactory/blocks.js
+++ b/demos/blockfactory/blocks.js
@@ -87,7 +87,9 @@ Blockly.Blocks['factory_base'] = {
     type.setShadow(true);
     type.outputConnection.connect(this.getInput(outputType).connection);
     type.initSvg();
-    type.render();
+    if (this.rendered) {
+      type.render();
+    }
   },
   updateShape_: function(option) {
     var outputExists = this.getInput('OUTPUTTYPE');