diff --git a/chrome/content/zotero/xpcom/utilities.js b/chrome/content/zotero/xpcom/utilities.js
index 0e937bd770..1f7c15902e 100644
--- a/chrome/content/zotero/xpcom/utilities.js
+++ b/chrome/content/zotero/xpcom/utilities.js
@@ -1660,7 +1660,9 @@ Zotero.Utilities = {
 	"itemToCSLJSON":function(zoteroItem) {
 		// If a Zotero.Item was passed, convert it to the proper format (skipping child items) and
 		// call this function again with that object
-		if (zoteroItem instanceof Zotero.Item) {
+		//
+		// (Zotero.Item won't be defined in translation-server)
+		if (typeof Zotero.Item !== 'undefined' && zoteroItem instanceof Zotero.Item) {
 			return this.itemToCSLJSON(
 				Zotero.Utilities.Internal.itemToExportFormat(zoteroItem, false, true)
 			);