diff --git a/lisp/image/gravatar.el b/lisp/image/gravatar.el
index f6f056a2ba..6fea19d942 100644
--- a/lisp/image/gravatar.el
+++ b/lisp/image/gravatar.el
@@ -41,15 +41,14 @@ gravatar-automatic-caching
   :group 'gravatar)
 (make-obsolete-variable 'gravatar-automatic-caching nil "28.1")
 
-(defcustom gravatar-cache-ttl 2592000
+(defcustom gravatar-cache-ttl 43200
   "Time to live in seconds for gravatar cache entries.
 If a requested gravatar has been cached for longer than this, it
-is retrieved anew.  The default value is 30 days."
+is retrieved anew.  The default value is 12 hours."
   :type 'integer
   ;; Restricted :type to number of seconds.
   :version "27.1"
   :group 'gravatar)
-(make-obsolete-variable 'gravatar-cache-ttl nil "28.1")
 
 (defcustom gravatar-rating "g"
   "Most explicit Gravatar rating level to allow.
@@ -287,8 +286,7 @@ gravatar-retrieve
 (defun gravatar--prune-cache ()
   (let ((expired nil)
         (time (- (time-convert (current-time) 'integer)
-                 ;; Twelve hours.
-                 (* 12 60 60))))
+                 gravatar-cache-ttl)))
     (maphash (lambda (key val)
                (when (< (car val) time)
                  (push key expired)))