2 files changed, 15 insertions, 7 deletions

diff --git a/lisp/gnus/gnus-group.el b/lisp/gnus/gnus-group.el
index b1a4933ebf1..9f272f42587 100644
--- a/lisp/gnus/gnus-group.el
+++ b/lisp/gnus/gnus-group.el
@@ -1396,7 +1396,8 @@ if it is a string, only list groups matching REGEXP."
       (gnus-group-prepare-flat-list-dead
        (gnus-union
         not-in-list
-        (setq gnus-killed-list (sort gnus-killed-list 'string<)))
+        (setq gnus-killed-list (sort gnus-killed-list 'string<))
+        :test 'equal)
        gnus-level-killed ?K regexp))
 
     (gnus-group-set-mode-line)
diff --git a/lisp/gnus/gnus-util.el b/lisp/gnus/gnus-util.el
index 40e2dcf92fd..6759c0715b7 100644
--- a/lisp/gnus/gnus-util.el
+++ b/lisp/gnus/gnus-util.el
@@ -1372,18 +1372,25 @@ Return the modified alist."
 
 (if (fboundp 'union)
     (defalias 'gnus-union 'union)
-  (defun gnus-union (l1 l2)
-    "Set union of lists L1 and L2."
+  (defun gnus-union (l1 l2 &rest keys)
+    "Set union of lists L1 and L2.
+If KEYS contains the `:test' and `equal' pair, use `equal' to compare
+items in lists, otherwise use `eq'."
     (cond ((null l1) l2)
           ((null l2) l1)
           ((equal l1 l2) l1)
           (t
            (or (>= (length l1) (length l2))
                (setq l1 (prog1 l2 (setq l2 l1))))
-           (while l2
-             (or (member (car l2) l1)
-                 (push (car l2) l1))
-             (pop l2))
+           (if (eq 'equal (plist-get keys :test))
+               (while l2
+                 (or (member (car l2) l1)
+                     (push (car l2) l1))
+                 (pop l2))
+             (while l2
+               (or (memq (car l2) l1)
+                   (push (car l2) l1))
+               (pop l2)))
            l1))))
 
 (declare-function gnus-add-text-properties "gnus"