diff --git a/lib/ransack/adapters/active_record.rb b/lib/ransack/adapters/active_record.rb
index 8782d84..a4ffc39 100644
--- a/lib/ransack/adapters/active_record.rb
+++ b/lib/ransack/adapters/active_record.rb
@@ -1,3 +1,4 @@
+require 'active_record'
 require 'ransack/adapters/active_record/base'
 ActiveRecord::Base.extend Ransack::Adapters::ActiveRecord::Base