Index: Story.js
===================================================================
--- Story.js	(revision 6578)
+++ Story.js	(working copy)
@@ -598,7 +598,7 @@
 		if(!store.tiddlerExists(newTitle))
 			minorUpdate = false;
 		var newDate = new Date();
-		var extendedFields = store.tiddlerExists(newTitle) ? store.fetchTiddler(newTitle).fields : (newTitle!=title && store.tiddlerExists(title) ? store.fetchTiddler(title).fields : config.defaultCustomFields);
+		var extendedFields = store.tiddlerExists(newTitle) ? store.fetchTiddler(newTitle).fields : (newTitle!=title && store.tiddlerExists(title) ? store.fetchTiddler(title).fields : merge({},config.defaultCustomFields));
 		for(var n in fields) {
 			if(!TiddlyWiki.isStandardField(n))
 				extendedFields[n] = fields[n];