--- /dev/null
+diff -up dhcp-4.2.4-P2/common/parse.c.dupl-key dhcp-4.2.4-P2/common/parse.c
+--- dhcp-4.2.4-P2/common/parse.c.dupl-key 2012-11-16 15:31:30.568561745 +0100
++++ dhcp-4.2.4-P2/common/parse.c 2012-11-16 15:31:30.577561619 +0100
+@@ -2893,6 +2893,9 @@ int parse_zone (struct dns_zone *zone, s
+ }
+ val = key_name;
+ }
++ if (zone->key)
++ log_fatal("Multiple key definition for zone %s.",
++ zone->name);
+ if (omapi_auth_key_lookup_name (&zone -> key, val) !=
+ ISC_R_SUCCESS)
+ parse_warn (cfile, "unknown key %s", val);