diff --git a/lualib/skynet/remotedebug.lua b/lualib/skynet/remotedebug.lua
index 7cfe19eb..72a06809 100644
--- a/lualib/skynet/remotedebug.lua
+++ b/lualib/skynet/remotedebug.lua
@@ -140,10 +140,13 @@ end
 local function watch_proto(protoname, cond)
 	local proto = assert(replace_upvalue(skynet.register_protocol, "proto"), "Can't find proto table")
 	local p = proto[protoname]
-	local dispatch = p.dispatch_origin or p.dispatch
-	if p == nil or dispatch == nil then
+	if p == nil then
 		return "No " .. protoname
 	end
+	local dispatch = p.dispatch_origin or p.dispatch
+	if dispatch == nil then
+		return "No dispatch"
+	end
 	p.dispatch_origin = dispatch
 	p.dispatch = function(...)
 		if not cond or cond(...) then