diff --git a/dm/dm/worker/server.go b/dm/dm/worker/server.go
index 14af90f9e38..b3f9b0ce51e 100644
--- a/dm/dm/worker/server.go
+++ b/dm/dm/worker/server.go
@@ -89,7 +89,7 @@ func NewServer(cfg *Config) *Server {
 }
 
 // Start starts to serving.
-// this function should only exit when can't dail DM-master, for other errors it should not exit
+// this function should only exit when can't dail DM-master, for other errors it should not exit.
 func (s *Server) Start() error {
 	log.L().Info("starting dm-worker server")
 	RegistryMetrics()