Protocol enumerable error

errors

[error] #PID<0.740.0> running Enterprise.Endpoint terminated
Server: localhost:4000 (http)
Request: GET /contracts/folders/4
** (exit) an exception was raised:
    ** (Protocol.UndefinedError) protocol Enumerable not implemented for "4". This protocol is implemented for: DBConnection.PrepareStream, DBConnection.Stream, Date.Range, Ecto.Adapters.SQL.Stream, File.Stream, Function, GenEvent.Stream, HashDict, HashSet, IO.Stream, List, Map, MapSet, Postgrex.Stream, Range, Stream, Timex.Interval
        (elixir) lib/enum.ex:1: Enumerable.impl_for!/1
        (elixir) lib/enum.ex:141: Enumerable.reduce/3
        (elixir) lib/enum.ex:1919: Enum.reduce/3
        (enterprise) web/router.ex:1: Enterprise.Router.Helpers.segments/3
        (enterprise) web/router.ex:1: Enterprise.Router.Helpers.api_contract_path/3
        (enterprise) web/templates/contract/footer.index.html.pug:29: Enterprise.ContractView."footer.index.html"/1
        (enterprise) web/templates/contract/folder/footer.html.pug:1: Enterprise.Contract.FolderView."footer.html"/1
        (enterprise) web/templates/layout/app.html.pug:39: Enterprise.LayoutView."app.html"/1
        (phoenix) lib/phoenix/view.ex:332: Phoenix.View.render_to_iodata/3
        (phoenix) lib/phoenix/controller.ex:740: Phoenix.Controller.do_render/4
        (enterprise) web/controllers/contract/folder_controller.ex:1: Enterprise.Contract.FolderController.action/2
        (enterprise) web/controllers/contract/folder_controller.ex:1: Enterprise.Contract.FolderController.phoenix_controller_pipeline/2
        (enterprise) lib/enterprise/endpoint.ex:1: Enterprise.Endpoint.instrument/4
        (phoenix) lib/phoenix/router.ex:278: Phoenix.Router.__call__/1
        (enterprise) lib/enterprise/endpoint.ex:1: Enterprise.Endpoint.plug_builder_call/2
        (enterprise) lib/plug/debugger.ex:99: Enterprise.Endpoint."call (overridable 3)"/2
        (enterprise) lib/enterprise/endpoint.ex:1: Enterprise.Endpoint.call/2
        (plug) lib/plug/adapters/cowboy/handler.ex:15: Plug.Adapters.Cowboy.Handler.upgrade/4
        (cowboy) /home/marbille/code/enterprise/deps/cowboy/src/cowboy_protocol.erl:442: :cowboy_protocol.execute/4