diff --git a/lisp/textmodes/bib-mode.el b/lisp/textmodes/bib-mode.el
index 82dd8cc785c..2d08506c4e3 100644
--- a/lisp/textmodes/bib-mode.el
+++ b/lisp/textmodes/bib-mode.el
@@ -34,6 +34,7 @@
 (defgroup bib nil
   "Major mode for editing bib files."
   :prefix "bib-"
+  :group 'external
   :group 'wp)
 
 (defcustom bib-file "~/my-bibliography.bib"