(gnus-summary-thread-gathering-function): Fix customize type.

diff --git a/lisp/gnus/gnus-sum.el b/lisp/gnus/gnus-sum.el
index 694e70a640a3a578e16dcb282a03969f08916334..9c751cd19d73215ff40fc0e8ee728a524407658a 100644 (file)
--- a/lisp/gnus/gnus-sum.el
+++ b/lisp/gnus/gnus-sum.el
@@ -136,9 +136,9 @@ which only takes Subjects into consideration; and
 `gnus-gather-threads-by-references', which compared the References
 headers of the articles to find matches."
   :group 'gnus-thread
-  :type '(set (function-item gnus-gather-threads-by-subject)
-             (function-item gnus-gather-threads-by-references)
-             (function :tag "other")))
+  :type '(radio (function-item gnus-gather-threads-by-subject)
+               (function-item gnus-gather-threads-by-references)
+               (function :tag "other")))
 
 ;; Added by Per Abrahamsen <amanda@iesd.auc.dk>.
 (defcustom gnus-summary-same-subject ""