diff --git a/lib/ransack/adapters.rb b/lib/ransack/adapters.rb
index 41cc2e6..8344f26 100644
--- a/lib/ransack/adapters.rb
+++ b/lib/ransack/adapters.rb
@@ -10,6 +10,8 @@ module Ransack
         ActiveRecordAdapter.new
       elsif defined?(::Mongoid)
         MongoidAdapter.new
+      else
+        raise "Unsupported adapter"
       end
     end