diff --git a/chrome/content/zotero/xpcom/data/itemFields.js b/chrome/content/zotero/xpcom/data/itemFields.js
index 650a04602b..c589560982 100644
--- a/chrome/content/zotero/xpcom/data/itemFields.js
+++ b/chrome/content/zotero/xpcom/data/itemFields.js
@@ -159,7 +159,8 @@ Zotero.ItemFields = new function() {
 	
 	
 	function isValidForType(fieldID, itemTypeID) {
-		_fieldCheck(fieldID, 'isValidForType');
+		fieldID = getID(fieldID);
+		if (!fieldID) return false;
 		
 		if (!_fields[fieldID]['itemTypes']) {
 			return false;