diff --git a/lib/cancan.rb b/lib/cancan.rb
index eb32c6e..e292895 100644
--- a/lib/cancan.rb
+++ b/lib/cancan.rb
@@ -10,4 +10,4 @@ require 'cancan/model_adapters/abstract_adapter'
 require 'cancan/model_adapters/default_adapter'
 require 'cancan/model_adapters/active_record_adapter' if defined? ActiveRecord
 require 'cancan/model_adapters/data_mapper_adapter' if defined? DataMapper
-require 'cancan/model_adapters/mongoid_adapter' if defined? Mongoid
+require 'cancan/model_adapters/mongoid_adapter' if defined?(Mongoid) && defined?(Mongoid::Document)