--- connection.c	2019-02-21 17:13:49.882419448 +0900
+++ connection.c.new	2019-02-21 17:13:34.090424889 +0900
@@ -430,6 +430,9 @@ begin_remote_xact(ConnCacheEntry *entry)
 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
 		else
 			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+		if (IsTransactionState()) {
+		    sql = "begin";
+		}
 		entry->changing_xact_state = true;
 		do_sql_command(entry->conn, sql);
 		entry->xact_depth = 1;