diff --git a/test/input_stream_test.rb b/test/input_stream_test.rb
index 773ee6b..1b69745 100644
--- a/test/input_stream_test.rb
+++ b/test/input_stream_test.rb
@@ -1,3 +1,4 @@
+require 'forwardable'
 require 'test_helper'

 class ZipInputStreamTest < MiniTest::Test