diff --git a/sshpiperd/config.go b/sshpiperd/config.go
index 8aae0e25..628f4ac6 100644
--- a/sshpiperd/config.go
+++ b/sshpiperd/config.go
@@ -82,7 +82,7 @@ func initConfig() {
 	pflag.StringVarP(&config.ListenAddr, "listen_addr", "l", "0.0.0.0", "Listening Address")
 	pflag.UintVarP(&config.Port, "port", "p", 2222, "Listening Port")
 	pflag.StringVarP(&config.WorkingDir, "working_dir", "w", "/var/sshpiper", "Working Dir")
-	pflag.StringVarP(&config.PiperKeyFile, "-server_key", "i", "/etc/ssh/ssh_host_rsa_key", "Key file for SSH Piper")
+	pflag.StringVarP(&config.PiperKeyFile, "server_key", "i", "/etc/ssh/ssh_host_rsa_key", "Key file for SSH Piper")
 	pflag.StringVarP(&config.Challenger, "challenger", "c", "", "Additional challenger name, e.g. pam, emtpy for no additional challenge")
 	pflag.StringVar(&config.Logfile, "log", "", "Logfile path. Leave emtpy or any error occurs will fall back to stdout")
 	pflag.BoolVar(&config.AllowBadUsername, "allow_bad_username", false, "disable username check while search the working dir")