diff --git a/src/calibre/library/check_library.py b/src/calibre/library/check_library.py
index 6b188afec2..f78912544b 100644
--- a/src/calibre/library/check_library.py
+++ b/src/calibre/library/check_library.py
@@ -21,7 +21,7 @@ CHECKS = [('invalid_titles',    _('Invalid titles')),
           ('extra_authors',     _('Extra authors')),
           ('missing_formats',   _('Missing book formats')),
           ('extra_formats',     _('Extra book formats')),
-          ('extra_files',       _('Unknown files in book')),
+          ('extra_files',       _('Unknown files in books')),
           ('failed_folders',    _('Folders raising exception'))
       ]