diff --git a/include/unistd.h b/include/unistd.h
index 1d0de4696322..47e06cbf979e 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -140,6 +140,7 @@ int	 initgroups __P((const char *, int));
 int	 iruserok __P((unsigned long, int, const char *, const char *));
 int	 issetugid __P((void));
 int	 lchown __P((const char *, uid_t, gid_t));
+char	*mkdtemp __P((char *));
 int	 mknod __P((const char *, mode_t, dev_t));
 int	 mkstemp __P((char *));
 char	*mktemp __P((char *));