diff --git a/lib/libc/sys/access.2 b/lib/libc/sys/access.2
index 65b8fb6bfbb..edc6194756c 100644
--- a/lib/libc/sys/access.2
+++ b/lib/libc/sys/access.2
@@ -133,8 +133,16 @@ and
 .Sh RETURN VALUES
 .Rv -std
 .Sh ERRORS
-Access to the file is denied if:
+.Fn access ,
+.Fn eaccess ,
+or
+.Fn faccessat 
+will fail if:
 .Bl -tag -width Er
+.It Bq Er EINVAL
+The value of the
+.Fa mode
+argument is invalid.
 .It Bq Er ENOTDIR
 A component of the path prefix is not a directory.
 .It Bq Er ENAMETOOLONG
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 1406e0f8bc5..b3b7ed5defd 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -2055,6 +2055,9 @@ kern_accessat(struct thread *td, int fd, char *path, enum uio_seg pathseg,
 	cap_rights_t rights;
 	int error;
 
+	if (amode != F_OK && (amode & ~(R_OK | W_OK | X_OK)) != 0)
+		return (EINVAL);
+
 	/*
 	 * Create and modify a temporary credential instead of one that
 	 * is potentially shared.