diff --git a/chrome/content/zotero/xpcom/schema.js b/chrome/content/zotero/xpcom/schema.js
index 5fd39e6e7..26857fa00 100644
--- a/chrome/content/zotero/xpcom/schema.js
+++ b/chrome/content/zotero/xpcom/schema.js
@@ -585,11 +585,14 @@ Zotero.Schema = new function(){
 			var deleted = xpiZipReader.getInputStream("deleted.txt");
 		}
 		
-		deleted = yield Zotero.File.getContentsAsync(deleted);
-		deleted = deleted.match(/^([^\s]+)/gm);
-		var version = deleted.shift();
+		let deletedVersion;
+		if (deleted) {
+			deleted = yield Zotero.File.getContentsAsync(deleted);
+			deleted = deleted.match(/^([^\s]+)/gm);
+			deletedVersion = deleted.shift();
+		}
 		
-		if (!lastVersion || lastVersion < version) {
+		if (!lastVersion || lastVersion < deletedVersion) {
 			var toDelete = [];
 			let iterator = new OS.File.DirectoryIterator(destDir);
 			try {