--- contrib/sendmail/src/conf.c
+++ contrib/sendmail/src/conf.c
@@ -5205,8 +5205,7 @@
 		return true;
 #else /* NETINET6 */
 	/* XXX how to correctly extract IN_LOOPBACKNET part? */
-	if (((ntohl(sa.sin.sin_addr.s_addr) & IN_CLASSA_NET)
-	     >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET)
+	if (IN_LOOPBACK(ntohl(sa.sin.sin_addr.s_addr)))
 		return true;
 #endif /* NETINET6 */
 	return false;