diff --git a/lib/libc/string/memchr.3 b/lib/libc/string/memchr.3
--- a/lib/libc/string/memchr.3
+++ b/lib/libc/string/memchr.3
@@ -52,7 +52,10 @@
 (converted to an
 .Vt "unsigned char" )
 in string
-.Fa b .
+.Fa b ,
+limited to at most
+.Fa len
+characters.
 .Pp
 The
 .Fn memrchr
@@ -61,15 +64,18 @@
 except that it locates the last occurrence of
 .Fa c
 in string
-.Fa b .
+.Fa b ,
+limited to the
+.Fa len
+characters.
 .Sh RETURN VALUES
 The
 .Fn memchr
 and
 .Fn memrchr
-functions
-return a pointer to the byte located,
-or NULL if no such byte exists within
+functions return a pointer to the byte located, or
+.Dv NULL
+if no such byte exists within
 .Fa len
 bytes.
 .Sh SEE ALSO