diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 989c4c8991..6313e11179 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1446,6 +1446,8 @@ class TestIO < Test::Unit::TestCase
       r.timeout = 0.1
       r2 = r.dup
       assert_equal(0.1, r2.timeout)
+    ensure
+      r2&.close
     end
   end