Unlock bundle from jekyll version

I get the following error:

$ bundle
Fetching gem metadata from https://rubygems.org/..........
Fetching gem metadata from https://rubygems.org/.
You have requested:
  jekyll ~> 3.8.5

The bundle currently has jekyll locked at 4.0.0.
Try running `bundle update jekyll`

If you are updating multiple gems in your Gemfile at once,
try passing them all to `bundle update

I am having some weird error having to to with githubpages discussed here:

(and perhaps here: https://github.com/github/pages-gem/issues/555)

any idea how to fix this?

I am currently trying to downgrade my jekyll version.

crossposted:

solution: delete the Gem.lock file