diff --git a/lualib-src/lua-cluster.c b/lualib-src/lua-cluster.c
index 586f74bf..e9d9e142 100644
--- a/lualib-src/lua-cluster.c
+++ b/lualib-src/lua-cluster.c
@@ -74,7 +74,7 @@ lpackrequest(lua_State *L) {
 		return luaL_error(L, "Invalid request message");
 	}
 	size_t sz = (size_t)luaL_checkinteger(L,4);
-	int session = luaL_optinteger(L,2,1);	// new connection start with 1
+	int session = luaL_checkinteger(L,2);
 	if (session <= 0) {
 		skynet_free(msg);
 		return luaL_error(L, "Invalid request session %d", session);
diff --git a/service/clusterd.lua b/service/clusterd.lua
index 3805be25..b0ee6335 100644
--- a/service/clusterd.lua
+++ b/service/clusterd.lua
@@ -62,7 +62,7 @@ function command.listen(source, addr, port)
 end
 
 local function send_request(source, node, addr, msg, sz)
-	local session = node_session[node]
+	local session = node_session[node] or 1
 	-- msg is a local pointer, cluster.packrequest will free it
 	local request, new_session = cluster.packrequest(addr, session, msg, sz)
 	local c = node_channel[node]