Authentication with Active Directory is returning true at all times

Question

    private bool AuthenticateAD(string username, string password)
    {
        try
        {
            using (PrincipalContext context = new PrincipalContext(ContextType.Domain, LDAP_DOMAIN))
            {
                return context.ValidateCredentials(username, password);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.StackTrace.ToString());
            return false;
        }
    }

The problem is that no matter what values I am passing to the method, it is always returning true No exception is being thrown. I have tried with real usernames and passwords as well as fake accounts.

I confirmed the account doesn't exist in AD.

Not sure what else I can do.