diff --git a/ChangeLog b/ChangeLog
index c29d25a6fa..4050ec4e53 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2017-12-23  Aurelien Jarno <aurelien@aurel32.net>
 
+	[BZ #21161]
+	* manual/arith.texi (strtoul): Fix a typo.
+
 	[BZ #22596]
 	* manual/arith.texi (finite): Fix the description of the return
 	value.
diff --git a/manual/arith.texi b/manual/arith.texi
index 4649bdf956..56ae6ddb35 100644
--- a/manual/arith.texi
+++ b/manual/arith.texi
@@ -2484,7 +2484,7 @@ in nearly all aspects but handles wide character strings.
 The @code{wcstol} function was introduced in @w{Amendment 1} of @w{ISO C90}.
 @end deftypefun
 
-@deftypefun {unsigned long int} strtoul (const char *retrict @var{string}, char **restrict @var{tailptr}, int @var{base})
+@deftypefun {unsigned long int} strtoul (const char *restrict @var{string}, char **restrict @var{tailptr}, int @var{base})
 @standards{ISO, stdlib.h}
 @safety{@prelim{}@mtsafe{@mtslocale{}}@assafe{}@acsafe{}}
 The @code{strtoul} (``string-to-unsigned-long'') function is like