Cant Change Owin LoginPath

hi

i used Owin Authentication for my mvc app. but Using Folowing code does not change Login path and yet an unauthorize request is redirting to /Account/Login

app.UseCookieAuthentication(new CookieAuthenticationOptions
            {
                AuthenticationType = "Application",
                AuthenticationMode = AuthenticationMode.Passive,
                LoginPath = new PathString("/MainPlugin/UserAccounts/Login")
            });

can any one tell me what is the problem