diff --git a/lisp/mail/rmail.el b/lisp/mail/rmail.el
index 4e182525511..4e5873c06ee 100644
--- a/lisp/mail/rmail.el
+++ b/lisp/mail/rmail.el
@@ -3403,7 +3403,7 @@ whitespace, replacing whitespace runs with a single space and
 removing prefixes such as Re:, Fwd: and so on and mailing list
 tags such as [tag]."
   (let ((subject (or (rmail-get-header "Subject" msgnum) ""))
-	(regexp "\`[ \t\n]*\\(\\(\\w\\{1,3\\}:\\|\\[[^]]+]\\)[ \t\n]+\\)*"))
+	(regexp "\\`[ \t\n]*\\(\\(\\w\\{1,3\\}:\\|\\[[^]]+]\\)[ \t\n]+\\)*"))
     (setq subject (rfc2047-decode-string subject))
     (setq subject (replace-regexp-in-string regexp "" subject))
     (replace-regexp-in-string "[ \t\n]+" " " subject)))