How to Fork an Unmaintained Ruby Gem for Rails 7

By USEO Engineering Team October 16, 2025

BLUF (Bottom Line Up Front): An abandoned gem restricting its dependencies to older Rails versions will block your upgrade. Instead of rewriting the functionality from scratch, the fastest path is to fork the unmaintained ruby gem, update its .gemspec to allow Rails 7, and point your Gemfile to your custom Git repository.

Phase 1: The Hardcoded Constraint

Glossary entry: Hardcoded Gem Dependencies.

Library authors often specify pessimistic version constraints (~> 6.0) in their gemspec. When Rails 7 is released, the gem still works perfectly fine logically, but Bundler refuses to install it.

Synthetic Engineering Context: The Abandoned Gem

# The Bad Code: Inside the abandoned gem's .gemspec
Gem::Specification.new do |spec|
  spec.name          = "legacy_csv_export"
  spec.version       = "2.1.0"
  
  # This hard constraint blocks the Rails 7 upgrade
  spec.add_dependency "activerecord", "< 7.0" 
end

Phase 2: The Fork and Patch Strategy

You must create a private or public fork of the repository, patch the constraint, and configure your application to use the modified version.

Execution: Patching the Gemspec

Fork the repository on GitHub to your organization.
Clone it locally and edit the .gemspec.

# The Fix: Relaxing the constraint in your fork
Gem::Specification.new do |spec|
  spec.name          = "legacy_csv_export"
  spec.version       = "2.1.1" # Bump the version
  
  # Allow Rails 7
  spec.add_dependency "activerecord", ">= 6.0", "< 8.0" 
end

Commit and push the changes to a specific branch in your fork.

Execution: Gemfile Override

Update your Rails application’s Gemfile to bypass RubyGems and fetch the code directly from your Git ref.

# Gemfile
# Pointing to the patched fork using a specific commit SHA or branch
gem 'legacy_csv_export', 
    git: 'https://github.com/your-org/legacy_csv_export.git', 
    branch: 'rails-7-support'

Run bundle install. Bundler will clone the repository and evaluate your patched gemspec.

Phase 3: Next Steps & Risk Mitigation

Forking is a temporary bridge, not a permanent architectural solution. By maintaining a fork, your team assumes responsibility for its security patches and future Ruby compatibility. You should schedule time to eventually replace abandoned gems legacy code with modern, maintained alternatives.

Need Help Stabilizing Your Legacy App? We maintain custom forks and backport security patches for critical enterprise dependencies. Our team at USEO secures your application when the open-source community moves on.