diff --git a/lisp/mail/mailalias.el b/lisp/mail/mailalias.el
index 42896c18ebe..8bb42634892 100644
--- a/lisp/mail/mailalias.el
+++ b/lisp/mail/mailalias.el
@@ -52,7 +52,11 @@ When t this still needs to be initialized.")
 (defvar mail-address-field-regexp
   "^\\(Resent-\\)?\\(To\\|From\\|Cc\\|Bcc\\|Reply-To\\):")
 
-(defvar pattern)
+;; `pattern' is bound dynamically before evaluating the forms in
+;; `mail-complete-alist' and may be part of user customizations of
+;; that variable.
+(with-suppressed-warnings ((lexical pattern))
+  (defvar pattern))
 
 (defcustom mail-complete-alist
   ;; Don't refer to mail-address-field-regexp here;