diff --git a/lib/irb/irb.gemspec b/lib/irb/irb.gemspec
index aba3f15675..9d889dfbf6 100644
--- a/lib/irb/irb.gemspec
+++ b/lib/irb/irb.gemspec
@@ -38,6 +38,7 @@ Gem::Specification.new do |spec|
     "lib/irb/cmd/pushws.rb",
     "lib/irb/cmd/subirb.rb",
     "lib/irb/color.rb",
+    "lib/irb/color_printer.rb",
     "lib/irb/completion.rb",
     "lib/irb/context.rb",
     "lib/irb/easter-egg.rb",