ecertfile error

I frequently get this error:

E(<0.225.0>:ejabberd_listener:131): Failed to open socket for {5223,
                                                               ejabberd_c2s,
                                                               [{access,c2s},
                                                                ssl,
                                                                {certfile,
                                                                    "./gentoo.pem"}]}: ecertfile

The certificate exists. I solve it by uncommenting the line before:

  %{5222, ejabberd_c2s,     [{access, c2s}, {shaper, c2s_shaper}]},

saving the configuration file, starting the server (and it does start as intented), stopping the server, and commenting the above line again. Now ejabberd start as expected. I doubt this is the correct way to deal with it though. Any help appreciated.