--- contrib/postgres_fdw/connection.c	2019-02-22 09:31:10.801333555 +0900
+++ contrib/postgres_fdw/connection.c.new	2019-02-22 09:31:04.153283090 +0900
@@ -429,7 +429,10 @@ begin_remote_xact(ConnCacheEntry *entry)
 		if (IsolationIsSerializable())
 			sql = "START TRANSACTION ISOLATION LEVEL SERIALIZABLE";
 		else
-			sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
+			if (XactIsoLevel == XACT_READ_COMMITTED) 
+				sql = "START TRANSACTION ISOLATION LEVEL READ COMMITTED";
+			else
+				sql = "START TRANSACTION ISOLATION LEVEL REPEATABLE READ";
 		entry->changing_xact_state = true;
 		do_sql_command(entry->conn, sql);
 		entry->xact_depth = 1;