diff --git a/chrome/content/zotero/xpcom/integration.js b/chrome/content/zotero/xpcom/integration.js
index 5817131e34..a1e8fe03b8 100644
--- a/chrome/content/zotero/xpcom/integration.js
+++ b/chrome/content/zotero/xpcom/integration.js
@@ -2659,6 +2659,7 @@ Zotero.Integration.Session.prototype.updateCitations = function(callback) {
 				index = parseInt(index);
 				
 				var citation = this.citationsByIndex[index];
+				if(!citation) continue;
 				if(citation.properties.delete) {
 					deleteCitations[index] = true;
 					continue;