Lapis errors with before filter.

app.lua

local lapis = require("lapis")
local app = lapis.Application()
local github_auth = require("github/auth");

app:enable("etlua")
app.layout = require("views.layout")

app:before_filter(function(self)
  if not self.current_user then
    self:write({
      redirect_to = github_auth.authentication_url_for(request, self:url_for("oauth_callback"))})
  end
end)

app:get("index", "/", function(self)
  return { render = "index" }
end)

app:get("oauth_callback", "/auth/callback", function(self)
  return "whateverrr"
end)

return app

ngx.log

2015/05/21 20:56:13 [error] 4731#0: *19 lua entry thread aborted: runtime error: ./app.lua:9: attempt to call field 'before_filter' (a nil value)
stack traceback:
coroutine 0:
        [C]: in function 'require'
        /home/steven/.luarocks/share/lua/5.1/lapis/init.lua:15: in function 'serve'
        content_by_lua(nginx.conf.compiled:23):2: in function <content_by_lua(nginx.conf.compiled:23):1>, client: 127.0.0.1, server: , request: "GET / HTTP/1.1", host: "localhost:8080"