diff --git a/activerecord/test/cases/schema_dumper_test.rb b/activerecord/test/cases/schema_dumper_test.rb
index 99e7ef6c03..71ff727b7f 100644
--- a/activerecord/test/cases/schema_dumper_test.rb
+++ b/activerecord/test/cases/schema_dumper_test.rb
@@ -1,5 +1,4 @@
 require "cases/helper"
-require 'stringio'
 
 
 class SchemaDumperTest < ActiveRecord::TestCase