diff --git a/chrome/content/zotero/xpcom/data/item.js b/chrome/content/zotero/xpcom/data/item.js
index 108d5b028..566db27ad 100644
--- a/chrome/content/zotero/xpcom/data/item.js
+++ b/chrome/content/zotero/xpcom/data/item.js
@@ -3191,7 +3191,9 @@ Zotero.Item.prototype.clone = function(includePrimary) {
 			if (this.attachmentPath) {
 				newItem.attachmentPath = this.attachmentPath;
 			}
-			newItem.attachmentSyncState = this.attachmentSyncState;
+			if (this.attachmentSyncState) {
+				newItem.attachmentSyncState = this.attachmentSyncState;
+			}
 		}
 	}