diff --git a/lisp/textmodes/bibtex-style.el b/lisp/textmodes/bibtex-style.el
index 99c2f92cab0..ee1a4f7d659 100644
--- a/lisp/textmodes/bibtex-style.el
+++ b/lisp/textmodes/bibtex-style.el
@@ -95,7 +95,8 @@
 
 (defcustom bibtex-style-indent-basic 2
   "Basic amount of indentation to use in BibTeX Style mode."
-  :type 'integer)
+  :type 'integer
+  :group 'bibtex)
 
 (defun bibtex-style-calculate-indentation (&optional virt)
   (or