diff --git a/demos/blockfactory/factory.js b/demos/blockfactory/factory.js
index ae215cd04..f6a9a5e4d 100644
--- a/demos/blockfactory/factory.js
+++ b/demos/blockfactory/factory.js
@@ -48,6 +48,7 @@ function formatChange() {
   var languagePre = document.getElementById('languagePre');
   var languageTA = document.getElementById('languageTA');
   if (document.getElementById('format').value == 'Manual') {
+    Blockly.hideChaff();
     mask.style.display = 'block';
     languagePre.style.display = 'none';
     languageTA.style.display = 'block';