diff -ur postfix-3.4.6.orig/src/dns/dns_str_resflags.c postfix-3.4.6/src/dns/dns_str_resflags.c
--- postfix-3.4.6.orig/src/dns/dns_str_resflags.c	2016-05-15 17:20:14.000000000 +0200
+++ postfix-3.4.6/src/dns/dns_str_resflags.c	2019-09-05 22:01:00.522000000 +0200
@@ -60,10 +60,16 @@
     "RES_DEFNAMES", RES_DEFNAMES,
     "RES_STAYOPEN", RES_STAYOPEN,
     "RES_DNSRCH", RES_DNSRCH,
+#ifdef RES_INSECURE1
     "RES_INSECURE1", RES_INSECURE1,
+#endif
+#ifdef RES_INSECURE2
     "RES_INSECURE2", RES_INSECURE2,
+#endif
     "RES_NOALIASES", RES_NOALIASES,
+#ifdef RES_USE_INET6
     "RES_USE_INET6", RES_USE_INET6,
+#endif
 #ifdef RES_ROTATE
     "RES_ROTATE", RES_ROTATE,
 #endif