diff --git a/rubocop.gemspec b/rubocop.gemspec
index 0e54f62f0d5..e7d598ee138 100644
--- a/rubocop.gemspec
+++ b/rubocop.gemspec
@@ -42,6 +42,4 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency('bundler', '>= 1.15.0', '< 3.0')
   s.add_development_dependency('rack', '>= 2.0')
-
-  s.post_install_message = File.read('manual/migrate_performance_cops.md')
 end