diff --git a/lib/slim_lint/linter/rubocop.rb b/lib/slim_lint/linter/rubocop.rb
index 1651f47..267ef66 100644
--- a/lib/slim_lint/linter/rubocop.rb
+++ b/lib/slim_lint/linter/rubocop.rb
@@ -4,6 +4,7 @@
 require_relative '../ruby_extract_engine'
 
 require 'rubocop'
+require 'stringio'
 
 module SlimLint
   # Runs RuboCop on Ruby code extracted from Slim templates.