diff --git a/lib/libc/sys/ioctl.2 b/lib/libc/sys/ioctl.2
index fe1fea2ac9a..f5e49d107a4 100644
--- a/lib/libc/sys/ioctl.2
+++ b/lib/libc/sys/ioctl.2
@@ -131,6 +131,9 @@ references.
 or
 .Fa argp
 is not valid.
+.It Bq Er EFAULT
+.Fa Argp
+points outside the process's allocated address space.
 .El
 .Sh SEE ALSO
 .Xr mt 1 ,