diff --git a/demos/blockfactory/app_controller.js b/demos/blockfactory/app_controller.js
index baf106ac7..ac69780b2 100644
--- a/demos/blockfactory/app_controller.js
+++ b/demos/blockfactory/app_controller.js
@@ -199,7 +199,9 @@ AppController.prototype.formatBlockLibraryForImport_ = function(xmlText) {
     xmlText = Blockly.Xml.domToText(xmlDom);
     // All block types should be lowercase.
     var blockType = this.getBlockTypeFromXml_(xmlText).toLowerCase();
-
+    // Some names are invalid so fix them up.
+    blockType = FactoryUtils.cleanBlockType(blockType);
+    
     blockXmlTextMap[blockType] = xmlText;
   }
 
diff --git a/demos/blockfactory/block_library_controller.js b/demos/blockfactory/block_library_controller.js
index fc5398c8c..1066ab127 100644
--- a/demos/blockfactory/block_library_controller.js
+++ b/demos/blockfactory/block_library_controller.js
@@ -64,8 +64,8 @@ BlockLibraryController = function(blockLibraryName, opt_blockLibraryStorage) {
 BlockLibraryController.prototype.getCurrentBlockType = function() {
   var rootBlock = FactoryUtils.getRootBlock(BlockFactory.mainWorkspace);
   var blockType = rootBlock.getFieldValue('NAME').trim().toLowerCase();
-  // Replace white space with underscores
-  return blockType.replace(/\W/g, '_').replace(/^(\d)/, '_\\1');
+  // Replace invalid characters.
+  return FactoryUtils.cleanBlockType(blockType);
 };
 
 /**
diff --git a/demos/blockfactory/factory_utils.js b/demos/blockfactory/factory_utils.js
index 89495d4ce..5da02f9c4 100644
--- a/demos/blockfactory/factory_utils.js
+++ b/demos/blockfactory/factory_utils.js
@@ -44,7 +44,7 @@ goog.provide('FactoryUtils');
  * @return {string} Block definition.
  */
 FactoryUtils.getBlockDefinition = function(blockType, rootBlock, format, workspace) {
-  blockType = blockType.replace(/\W/g, '_').replace(/^(\d)/, '_\\1');
+  blockType = FactoryUtils.cleanBlockType(blockType);
   switch (format) {
     case 'JSON':
       var code = FactoryUtils.formatJson_(blockType, rootBlock);
@@ -56,6 +56,19 @@ FactoryUtils.getBlockDefinition = function(blockType, rootBlock, format, workspa
   return code;
 };
 
+/**
+ * Convert invalid block name to a valid one. Replaces whitespace
+ * and prepend names that start with a digit with an '_'.
+ * @param {string} blockType Type of block.
+ * @return {string} Cleaned up block type.
+ */
+FactoryUtils.cleanBlockType = function(blockType) {
+  if (!blockType) {
+    return '';
+  }
+  return blockType.replace(/\W/g, '_').replace(/^(\d)/, '_$1');
+};
+
 /**
  * Get the generator code for a given block.
  * @param {!Blockly.Block} block Rendered block in preview workspace.