diff -up openssh-5.9p1/dns.c.edns openssh-5.9p1/dns.c
--- openssh-5.9p1/dns.c.edns	2010-08-31 14:41:14.000000000 +0200
+++ openssh-5.9p1/dns.c	2011-09-09 08:05:27.782440497 +0200
@@ -177,6 +177,7 @@ verify_host_key_dns(const char *hostname
 {
 	u_int counter;
 	int result;
+	unsigned int rrset_flags = 0;
 	struct rrsetinfo *fingerprints = NULL;
 
 	u_int8_t hostkey_algorithm;
@@ -200,8 +201,19 @@ verify_host_key_dns(const char *hostname
 		return -1;
 	}
 
+	/*
+	 * Original getrrsetbyname function, found on OpenBSD for example,
+	 * doesn't accept any flag and prerequisite for obtaining AD bit in
+	 * DNS response is set by "options edns0" in resolv.conf.
+	 *
+	 * Our version is more clever and use RRSET_FORCE_EDNS0 flag.
+	 */
+#ifndef HAVE_GETRRSETBYNAME
+	rrset_flags |= RRSET_FORCE_EDNS0;
+#endif
 	result = getrrsetbyname(hostname, DNS_RDATACLASS_IN,
-	    DNS_RDATATYPE_SSHFP, 0, &fingerprints);
+	    DNS_RDATATYPE_SSHFP, rrset_flags, &fingerprints);
+
 	if (result) {
 		verbose("DNS lookup error: %s", dns_result_totext(result));
 		return -1;
diff -up openssh-5.9p1/openbsd-compat/getrrsetbyname.c.edns openssh-5.9p1/openbsd-compat/getrrsetbyname.c
--- openssh-5.9p1/openbsd-compat/getrrsetbyname.c.edns	2009-07-13 03:38:23.000000000 +0200
+++ openssh-5.9p1/openbsd-compat/getrrsetbyname.c	2011-09-09 15:03:39.930500801 +0200
@@ -209,8 +209,8 @@ getrrsetbyname(const char *hostname, uns
 		goto fail;
 	}
 
-	/* don't allow flags yet, unimplemented */
-	if (flags) {
+	/* Allow RRSET_FORCE_EDNS0 flag only. */
+	if ((flags & ~RRSET_FORCE_EDNS0) != 0) {
 		result = ERRSET_INVAL;
 		goto fail;
 	}
@@ -226,9 +226,9 @@ getrrsetbyname(const char *hostname, uns
 #endif /* DEBUG */
 
 #ifdef RES_USE_DNSSEC
-	/* turn on DNSSEC if EDNS0 is configured */
-	if (_resp->options & RES_USE_EDNS0)
-		_resp->options |= RES_USE_DNSSEC;
+	/* turn on DNSSEC if required  */
+	if (flags & RRSET_FORCE_EDNS0)
+		_resp->options |= (RES_USE_EDNS0|RES_USE_DNSSEC);
 #endif /* RES_USE_DNSEC */
 
 	/* make query */
diff -up openssh-5.9p1/openbsd-compat/getrrsetbyname.h.edns openssh-5.9p1/openbsd-compat/getrrsetbyname.h
--- openssh-5.9p1/openbsd-compat/getrrsetbyname.h.edns	2007-10-26 08:26:50.000000000 +0200
+++ openssh-5.9p1/openbsd-compat/getrrsetbyname.h	2011-09-09 08:05:27.965438689 +0200
@@ -72,6 +72,9 @@
 #ifndef RRSET_VALIDATED
 # define RRSET_VALIDATED	1
 #endif
+#ifndef RRSET_FORCE_EDNS0
+# define RRSET_FORCE_EDNS0	0x0001
+#endif
 
 /*
  * Return codes for getrrsetbyname()