diff --git a/lib/reline/reline.gemspec b/lib/reline/reline.gemspec
index 0a0b129228..763c0f8bc3 100644
--- a/lib/reline/reline.gemspec
+++ b/lib/reline/reline.gemspec
@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.homepage      = 'https://github.com/ruby/reline'
   spec.license       = 'Ruby'
 
-  spec.files         = Dir['BSDL', 'COPYING', 'README.md', 'lib/**/*']
+  spec.files         = Dir['BSDL', 'COPYING', 'README.md', 'license_of_rb-readline', 'lib/**/*']
   spec.require_paths = ['lib']
 
   spec.required_ruby_version = Gem::Requirement.new('>= 2.5')