# File lib/omniauth/strategies/oauth2/gowalla.rb, line 84
    def build_access_token
      token=super
      ##remove expires_at from token, invalid format
      token=::OAuth2::AccessToken.new(token.client,token.token,{:expires_in=>token.expires_in,:refresh_token=>token.refresh_token}.merge(token.params))
      ## if token is expired refresh and again remove expires_at
      if token.expired?
        token=token.refresh!
        token=::OAuth2::AccessToken.new(token.client,token.token,{:expires_in=>token.expires_in,:refresh_token=>token.refresh_token}.merge(token.params))
      end
      token
      
    end