diff --git a/otherlibs/unix/unix.mli b/otherlibs/unix/unix.mli
index d8a1575..f4ec9e3 100644
--- a/otherlibs/unix/unix.mli
+++ b/otherlibs/unix/unix.mli
@@ -912,6 +912,8 @@ val inet6_addr_any : inet_addr
 val inet6_addr_loopback : inet_addr
 (** A special IPv6 address representing the host machine ([::1]). *)

+val is_inet6_addr : inet_addr -> bool
+(** Test if an IP address is an IPv6 address. *)

 (** {6 Sockets} *)