diff --git a/lib/torch.rb b/lib/torch.rb
index 346e2d2..9d591eb 100644
--- a/lib/torch.rb
+++ b/lib/torch.rb
@@ -4,6 +4,7 @@
 # stdlib
 require "fileutils"
 require "net/http"
+require "set"
 require "tmpdir"
 
 # native functions