diff --git a/chrome/content/zotero/xpcom/attachments.js b/chrome/content/zotero/xpcom/attachments.js
index 7722b889b..ec98767d9 100644
--- a/chrome/content/zotero/xpcom/attachments.js
+++ b/chrome/content/zotero/xpcom/attachments.js
@@ -891,7 +891,7 @@ Zotero.Attachments = new function(){
 				break;
 				
 				default:
-					var value = item.getField(field, false, true);
+					var value = '' + item.getField(field, false, true);
 			}
 			
 			var re = new RegExp("\{?([^%\{\}]*)" + rpl + "(\{[0-9]+\})?" + "([^%\{\}]*)\}?");