diff --git a/lualib/skynet.lua b/lualib/skynet.lua
index a5353a03..9a590d1d 100644
--- a/lualib/skynet.lua
+++ b/lualib/skynet.lua
@@ -489,6 +489,8 @@ local function raw_dispatch_message(prototype, msg, sz, session, source)
 			session_coroutine_id[co] = session
 			session_coroutine_address[co] = source
 			suspend(co, coroutine_resume(co, session,source, p.unpack(msg,sz)))
+		elseif session ~= 0 then
+			c.send(source, skynet.PTYPE_ERROR, session, "")
 		else
 			unknown_request(session, source, msg, sz, proto[prototype].name)
 		end