diff --git a/test/jruby/test_io.rb b/test/jruby/test_io.rb
index 746eb035ba0..f72cfde2b1d 100644
--- a/test/jruby/test_io.rb
+++ b/test/jruby/test_io.rb
@@ -3,6 +3,7 @@
 require 'test/jruby/test_helper'
 require 'rbconfig'
 require 'stringio'
+require 'tempfile'
 
 class TestIO < Test::Unit::TestCase
   include TestHelper