--- a/configure.in
+++ b/configure.in
@@ -84,15 +84,26 @@
 dnl #######################
 dnl Checks for header files
 dnl #######################
 AC_HEADER_STDC
 AC_HEADER_SYS_WAIT
-AC_CHECK_HEADERS(sys/time.h sys/stat.h unistd.h strings.h fcntl.h netinet/ip6.h)
+AC_CHECK_HEADERS(sys/time.h sys/stat.h unistd.h strings.h fcntl.h)
 
 dnl BSD/OS Seems to not have a good ethernet header, so we gotta wing it
 AC_CHECK_HEADERS(net/if.h net/ethernet.h netinet/if_ether.h net/ppp_defs.h)
 
+AC_ARG_ENABLE( ipv6, [ AC_HELP_STRING([--enable-ipv6], [s use IPv6?]) ], ip6=$enableval )
+if test "$ip6" = "yes"
+then
+	AC_CHECK_HEADER(netinet/ip6.h, , [AC_MSG_ERROR([I couldn't find netinet/ip6.h though you asked for ipv6 support.])] )
+elif test "$ip6" != "no"
+then
+	AC_CHECK_HEADER(netinet/ip6.h)
+
+fi
+
+
 dnl #############################################################
 dnl Checks for typedefs, structures, and compiler characteristics
 dnl #############################################################
 AC_C_CONST
 AC_TYPE_SIZE_T