diff --git a/test/irb/helper.rb b/test/irb/helper.rb
index 56ec1a8374..e4ce7bff08 100644
--- a/test/irb/helper.rb
+++ b/test/irb/helper.rb
@@ -1,4 +1,6 @@
 require "test/unit"
+require "pathname"
+
 begin
   require_relative "../lib/helper"
 rescue LoadError # ruby/ruby defines helpers differently