diff --git a/vtysh/vtysh_user.c b/vtysh/vtysh_user.c
index 9233010..f84cca8 100644
--- a/vtysh/vtysh_user.c
+++ b/vtysh/vtysh_user.c
@@ -46,7 +46,7 @@
 };
 
 int
-vtysh_pam (char *user)
+vtysh_pam (const char *user)
 {
   int ret;
   pam_handle_t *pamh = NULL;
@@ -114,7 +114,7 @@
 }
 
 struct user *
-user_lookup (char *name)
+user_lookup (const char *name)
 {
   struct listnode *nn;
   struct user *user;
@@ -141,7 +141,7 @@
 }
 
 struct user *
-user_get (char *name)
+user_get (const char *name)
 {
   struct user *user;
   user = user_lookup (name);