diff --git a/src/calibre/utils/search_query_parser.py b/src/calibre/utils/search_query_parser.py
index 05e0ed3e8f..35241c89c4 100644
--- a/src/calibre/utils/search_query_parser.py
+++ b/src/calibre/utils/search_query_parser.py
@@ -52,6 +52,7 @@ class SearchQueryParser(object):
         'series',
         'comments',
         'format',
+        'isbn',
         'all',
                  ]