diff --git a/lib/unicorn/worker_killer.rb b/lib/unicorn/worker_killer.rb
index 389407c..c2cabbd 100644
--- a/lib/unicorn/worker_killer.rb
+++ b/lib/unicorn/worker_killer.rb
@@ -1,3 +1,4 @@
+require 'unicorn'
 require 'unicorn/worker_killer/configuration'
 require 'get_process_mem'