diff --git a/acinclude.m4 b/acinclude.m4
index 86f1c61f8..0563c130e 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -668,4 +668,14 @@ if test "$ac_cv_func_vsnprintf_working" = yes; then
 	foo=HAVE_VSNPRINTF
 	AC_DEFINE_UNQUOTED($foo)
 fi
-])
\ No newline at end of file
+])
+
+AC_DEFUN(AC_KRB_IPV6, [
+AC_MSG_CHECKING(for IPv6)
+foo=no
+AC_EGREP_HEADER(sockaddr_in6, netinet/in.h,
+AC_DEFINE(HAVE_STRUCT_SOCKADDR_IN6) foo=yes)
+AC_EGREP_HEADER(sockaddr_in6, netinet/in6.h,
+AC_DEFINE(HAVE_STRUCT_SOCKADDR_IN6) foo=yes)
+AC_MSG_RESULT($foo)
+])