diff --git a/demos/blockfactory/blocks.js b/demos/blockfactory/blocks.js
index 52172f5db..3a3101956 100644
--- a/demos/blockfactory/blocks.js
+++ b/demos/blockfactory/blocks.js
@@ -696,7 +696,10 @@ Blockly.Blocks['colour_hue'] = {
   },
   validator: function(text) {
     // Update the current block's colour to match.
-    this.sourceBlock_.setColour(text);
+    var hue = parseInt(text, 10);
+    if (!isNaN(hue)) {
+      this.sourceBlock_.setColour(hue);
+    }
   },
   mutationToDom: function(workspace) {
     var container = document.createElement('mutation');
diff --git a/demos/blockfactory/factory.js b/demos/blockfactory/factory.js
index 6182a5b26..c8dc2e0ba 100644
--- a/demos/blockfactory/factory.js
+++ b/demos/blockfactory/factory.js
@@ -258,7 +258,9 @@ function formatJavaScript_(blockType, rootBlock) {
   var colourBlock = rootBlock.getInputTargetBlock('COLOUR');
   if (colourBlock && !colourBlock.disabled) {
     var hue = parseInt(colourBlock.getFieldValue('HUE'), 10);
-    code.push('    this.setColour(' + hue + ');');
+    if (!isNaN(hue)) {
+      code.push('    this.setColour(' + hue + ');');
+    }
   }
   code.push("    this.setTooltip('');");
   code.push("    this.setHelpUrl('http://www.example.com/');");