diff --git a/chrome/content/zotero/xpcom/sync/syncExceptions.js b/chrome/content/zotero/xpcom/sync/syncExceptions.js
new file mode 100644
index 0000000000..473e017fe6
--- /dev/null
+++ b/chrome/content/zotero/xpcom/sync/syncExceptions.js
@@ -0,0 +1,41 @@
+/*
+    ***** BEGIN LICENSE BLOCK *****
+    
+    Copyright © 2016 Center for History and New Media
+                     George Mason University, Fairfax, Virginia, USA
+                     http://zotero.org
+    
+    This file is part of Zotero.
+    
+    Zotero is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+    
+    Zotero is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+    
+    You should have received a copy of the GNU Affero General Public License
+    along with Zotero.  If not, see <http://www.gnu.org/licenses/>.
+    
+    ***** END LICENSE BLOCK *****
+*/
+
+"use strict";
+
+/**
+ * @param {Boolean} [advanceToNextLibrary=false] - If true, continue with next library; if false, stop
+ *     sync completely
+ */
+Zotero.Sync.UserCancelledException = function (advanceToNextLibrary) {
+	this.message = "Sync cancelled";
+	this.advanceToNextLibrary = advanceToNextLibrary;
+}
+
+Zotero.Sync.UserCancelledException.prototype = Object.create(Error.prototype);
+
+Zotero.Sync.UserCancelledException.prototype.toString = function() {
+	return this.message;
+};