diff --git a/chrome/content/zotero/xpcom/duplicates.js b/chrome/content/zotero/xpcom/duplicates.js
index 245f0939cb..41d50c2a04 100644
--- a/chrome/content/zotero/xpcom/duplicates.js
+++ b/chrome/content/zotero/xpcom/duplicates.js
@@ -202,7 +202,7 @@ Zotero.Duplicates.prototype._findDuplicates = function () {
 	// DOI
 	var sql = "SELECT itemID, value FROM items JOIN itemData USING (itemID) "
 				+ "JOIN itemDataValues USING (valueID) "
-				+ "WHERE libraryID=? AND fieldID=? AND REGEXP('^10\.', value) "
+				+ "WHERE libraryID=? AND fieldID=? AND REGEXP('^10\\.', value) "
 				+ "AND itemID NOT IN (SELECT itemID FROM deletedItems) "
 				+ "ORDER BY value";
 	var rows = Zotero.DB.query(sql, [this._libraryID, Zotero.ItemFields.getID('DOI')]);