diff --git a/lib/libc/locale/islower.3 b/lib/libc/locale/islower.3
index 019e612d8383..b2cca524dd27 100644
--- a/lib/libc/locale/islower.3
+++ b/lib/libc/locale/islower.3
@@ -67,6 +67,7 @@ function returns zero if the character tests false and
 returns non-zero if the character tests true.
 .Sh SEE ALSO
 .Xr ctype 3 ,
+.Xr tolower 3 ,
 .Xr ascii 7
 .Sh STANDARDS
 The
diff --git a/lib/libc/locale/isupper.3 b/lib/libc/locale/isupper.3
index 7d09f4423032..77b76befdca5 100644
--- a/lib/libc/locale/isupper.3
+++ b/lib/libc/locale/isupper.3
@@ -67,6 +67,7 @@ function returns zero if the character tests false and
 returns non-zero if the character tests true.
 .Sh SEE ALSO
 .Xr ctype 3 ,
+.Xr toupper 3 ,
 .Xr ascii 7
 .Sh STANDARDS
 The