diff --git a/test/rdoc/test_rdoc_generator_darkfish.rb b/test/rdoc/test_rdoc_generator_darkfish.rb
index 352e9336ff..bbe351c0f6 100644
--- a/test/rdoc/test_rdoc_generator_darkfish.rb
+++ b/test/rdoc/test_rdoc_generator_darkfish.rb
@@ -215,6 +215,7 @@ class TestRDocGeneratorDarkfish < RDoc::TestCase
     method_name_index = internal_file.index('<span class="method-name">method_with_html_tag_yield</span>')
     last_of_method_name_index = method_name_index + internal_file[method_name_index..-1].index('<div class="method-description">') - 1
     method_name = internal_file[method_name_index..last_of_method_name_index]
+    f.close
 
     assert_includes method_name, '{ |%&lt;&lt;script&gt;alert(&quot;atui&quot;)&lt;/script&gt;&gt;, yield_arg| ... }'
   end