class Bundler::StubSpecification

def source=(source)
  super
  # Stub has no concept of source, which means that extension_dir may be wrong
  # This is the case for git-based gems. So, instead manually assign the extension dir
  return unless source.respond_to?(:extension_dir_name)
  path = File.join(stub.extensions_dir, source.extension_dir_name)
  stub.extension_dir = File.expand_path(path)
end