Gitlab rbtrace debugging


I have followed a tutorial to use a rbtrace, but it seems that I am doing something wrong. I have added gitlab_rails['env'] = {"ENABLE_RBTRACE" => "1"} to the gitlab config and then called /opt/gitlab/embedded/bin/ruby /opt/gitlab/embedded/bin/rbtrace --methods somemethod but it gives me an error:

**Traceback** (most recent call last):

3: from /opt/gitlab/embedded/bin/rbtrace:23:in `<main>'

2: from /opt/gitlab/embedded/bin/rbtrace:23:in `load'

1: from /opt/gitlab/embedded/lib/ruby/gems/2.6.0/gems/rbtrace-0.4.11/bin/rbtrace:5:in `<top (required)>'

/opt/gitlab/embedded/lib/ruby/gems/2.6.0/gems/rbtrace-0.4.11/lib/rbtrace/cli.rb:373:in `run': **undefined method `size' for nil:NilClass (** **NoMethodError** **)**

I also tried to attach to a PID, but it seems that rbtrace is not still supported.

And yes I have reconfigured and restarted whole gitlab.

Thank you for your help.