diff --git a/Library/Homebrew/cask/utils.rb b/Library/Homebrew/cask/utils.rb
index 74a531025b..c512e898d6 100644
--- a/Library/Homebrew/cask/utils.rb
+++ b/Library/Homebrew/cask/utils.rb
@@ -3,7 +3,6 @@
 
 require "utils/user"
 require "open3"
-require "stringio"
 
 BUG_REPORTS_URL = "https://github.com/Homebrew/homebrew-cask#reporting-bugs"