Doesn't seem to work without google-protobuf

Using this in a new project I noticed it doesn't successfully load unless google-protobuf is present. Toy demonstration from irb:

james@black-lagoon ~ % irb
irb(main):001> require 'cel'
=> true
irb(main):002> require "google/protobuf"
=> false
irb(main):003> 
james@black-lagoon ~ % gem list | grep google
google-protobuf (3.24.0 ruby arm64-darwin, 3.23.4 arm64-darwin)
james@black-lagoon ~ % gem uninstall google-protobuf

Select gem to uninstall:
 1. google-protobuf-3.23.4-arm64-darwin
 2. google-protobuf-3.24.0
 3. google-protobuf-3.24.0-arm64-darwin
 4. All versions
> 4
Successfully uninstalled google-protobuf-3.23.4-arm64-darwin
Successfully uninstalled google-protobuf-3.24.0
Successfully uninstalled google-protobuf-3.24.0-arm64-darwin
james@black-lagoon ~ % irb                          
irb(main):001> require 'cel'
<internal:/Users/james/.rbenv/versions/3.2.2/lib/ruby/site_ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:86:in `require': cannot load such file -- google/protobuf/struct_pb (LoadError)

Not a big deal as I simply installed protobuf and it's fine, but it's not currently optional.