diff --git a/ext/socket/option.c b/ext/socket/option.c
index cd7cd8e2e7..96cc8b440f 100644
--- a/ext/socket/option.c
+++ b/ext/socket/option.c
@@ -426,8 +426,11 @@ inspect_timeval_as_interval(int level, int optname, VALUE data, VALUE ret)
  * Another hackish workaround is "RFC 1724 hack".
  * RFC 1724 section 3.3 suggests unnumbered interfaces
  * specified by pseudo address 0.0.0.0/8.
- * NetBSD 4 documented it.
+ * NetBSD 4 and FreeBSD 5 documented it.
  * http://cvsweb.netbsd.org/cgi-bin/cvsweb.cgi/src/share/man/man4/ip.4.diff?r1=1.16&r2=1.17
+ * http://www.FreeBSD.org/cgi/cvsweb.cgi/src/share/man/man4/ip.4.diff?r1=1.37;r2=1.38
+ * FreeBSD 7.0 reomved it.
+ * http://www.FreeBSD.org/cgi/cvsweb.cgi/src/share/man/man4/ip.4.diff?r1=1.49;r2=1.50
  *
  * RFC 1724 hack is not supported by Socket::Option#inspect because
  * it is not distinguishable by the size.