diff --git a/contrib/uuid-ossp/expected/uuid_ossp.out b/contrib/uuid-ossp/expected/uuid_ossp.out
index f393e86..c14db22 100644
--- a/contrib/uuid-ossp/expected/uuid_ossp.out
+++ b/contrib/uuid-ossp/expected/uuid_ossp.out
@@ -77,3 +77,18 @@ SELECT uuid_generate_v4()::text ~ '^[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]
  t
 (1 row)
 
+DO $_$
+DECLARE
+  u text;
+  i int;
+  c int;
+BEGIN
+  FOR i in 1..32 LOOP
+    u := substr(uuid_generate_v1mc()::text, 25, 2);
+    EXECUTE 'SELECT x''' || u || '''::int & 3' INTO c;
+    IF c <> 3 THEN
+      RAISE WARNING 'v1mc broken';
+    END IF;
+  END LOOP;
+END;
+$_$;
diff --git a/contrib/uuid-ossp/sql/uuid_ossp.sql b/contrib/uuid-ossp/sql/uuid_ossp.sql
index 8f22417..61a44a8 100644
--- a/contrib/uuid-ossp/sql/uuid_ossp.sql
+++ b/contrib/uuid-ossp/sql/uuid_ossp.sql
@@ -17,3 +17,20 @@ SELECT uuid_generate_v3(uuid_ns_dns(), 'www.widgets.com');
 SELECT uuid_generate_v5(uuid_ns_dns(), 'www.widgets.com');
 
 SELECT uuid_generate_v4()::text ~ '^[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}$';
+
+DO $_$
+DECLARE
+  u text;
+  i int;
+  c int;
+BEGIN
+  FOR i in 1..32 LOOP
+    u := substr(uuid_generate_v1mc()::text, 25, 2);
+    EXECUTE 'SELECT x''' || u || '''::int & 3' INTO c;
+    IF c <> 3 THEN
+      RAISE WARNING 'v1mc broken';
+    END IF;
+  END LOOP;
+END;
+$_$;
+
diff --git a/contrib/uuid-ossp/uuid-ossp.c b/contrib/uuid-ossp/uuid-ossp.c
index bc29ade..7803dbe 100644
--- a/contrib/uuid-ossp/uuid-ossp.c
+++ b/contrib/uuid-ossp/uuid-ossp.c
@@ -460,6 +460,10 @@ uuid_generate_v1mc(PG_FUNCTION_ARGS)
 	uuid_t		uu;
 
 	uuid_generate_random(uu);
+
+	/* set IEEE802 multicast and local-admin bits */
+	((dce_uuid_t *)&uu)->node[0] |= 0x03;
+
 	uuid_unparse(uu, strbuf);
 	buf = strbuf + 24;
 #else							/* BSD */
@@ -472,7 +476,7 @@ uuid_generate_v1mc(PG_FUNCTION_ARGS)
 #endif
 
 	return uuid_generate_internal(UUID_MAKE_V1 | UUID_MAKE_MC, NULL,
-								  buf, buf ? 13 : 0);
+								  buf, 13);
 }