diff --git a/chrome/content/zotero/xpcom/integration.js b/chrome/content/zotero/xpcom/integration.js
index 1e37684303..5314992e10 100644
--- a/chrome/content/zotero/xpcom/integration.js
+++ b/chrome/content/zotero/xpcom/integration.js
@@ -1660,7 +1660,7 @@ Zotero.Integration.Session.prototype.getCiteprocLists = function() {
 			continue;
 		}
 		citations.push([this.citationsByIndex[idx].citationID, this.citationsByIndex[idx].properties.noteIndex]);
-		fieldToCitationIdxMapping[i] = idx;
+		fieldToCitationIdxMapping[i] = parseInt(idx);
 		citationToFieldIdxMapping[idx] = i++;
 	}
 	return [citations, fieldToCitationIdxMapping, citationToFieldIdxMapping];