diff --git a/lib/irb/history.rb b/lib/irb/history.rb
index ad17347fb..dffdee32d 100644
--- a/lib/irb/history.rb
+++ b/lib/irb/history.rb
@@ -1,3 +1,5 @@
+require "pathname"
+
 module IRB
   module HistorySavingAbility # :nodoc:
     def support_history_saving?