Jekyll 4.2.0 won't serve -- can't find gem file

[davidhoyle]

I can install and build:
dhoyle-MBP15-10566:myblog dhoyle$ jekyll -v
jekyll 4.2.0
dhoyle-MBP15-10566:myblog dhoyle$ which ruby
/usr/local/opt/ruby/bin/ruby
dhoyle-MBP15-10566:myblog dhoyle$ ruby -v
ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin18]
dhoyle-MBP15-10566:myblog dhoyle$ gem -v
3.2.4
dhoyle-MBP15-10566:myblog dhoyle$

But I can't serve, I get:

dhoyle-MBP15-10566:myblog dhoyle$ bundle exec jekyll serve
Configuration file: /Users/dhoyle/myblog/_config.yml
Source: /Users/dhoyle/myblog
Destination: /Users/dhoyle/myblog/_site
Incremental build: disabled. Enable with --incremental
Generating...
Jekyll Feed: Generating feed for posts
done in 0.27 seconds.
Auto-regeneration: enabled for '/Users/dhoyle/myblog'
------------------------------------------------
Jekyll 4.2.0 Please append --trace to the serve command
for any additional information or backtrace.
------------------------------------------------
/usr/local/lib/ruby/gems/3.0.0/gems/jekyll-4.2.0/lib/jekyll/commands/serve/servlet.rb:3:in require': cannot load such file -- webrick (LoadError) from /usr/local/lib/ruby/gems/3.0.0/gems/jekyll-4.2.0/lib/jekyll/commands/serve/servlet.rb:3:in <top (required)>'

I tried:
sudo rm -rf _site
bundle update
bundle exec jekyll serve

But I'm still getting the same error. Can you tell me how I can get/load that file so jekyll serve will work?

[ashmaroli]

run bundle add webrick.

[davidhoyle]

That worked, thanks very much @ashmaroli!

[kmk3]

Duplicate of #8523.

[lazydeveloper]

run bundle add webrick.

worked like a charm for me. Thanks!