diff --git a/lib/prodder/pg.rb b/lib/prodder/pg.rb
index 1940187..2d19823 100644
--- a/lib/prodder/pg.rb
+++ b/lib/prodder/pg.rb
@@ -1,5 +1,6 @@
 require 'open3'
 require 'pg'
+require 'set'
 
 module Prodder
   class PG