diff --git a/CHANGELOG.rdoc b/CHANGELOG.rdoc
index 35b3bcd6..a7cdd574 100644
--- a/CHANGELOG.rdoc
+++ b/CHANGELOG.rdoc
@@ -2,6 +2,10 @@ Develop
 
 Unreleased
 
+1.17.0 (March 26th, 2017)
+
+* Improve performance for the Mongoid Adapter
+
 1.16.0 (February 2nd, 2017)
 
 * Introduce rubocop and fixes most of the issues
diff --git a/lib/cancan/model_adapters/mongoid_adapter.rb b/lib/cancan/model_adapters/mongoid_adapter.rb
index 1771de11..87eff16b 100644
--- a/lib/cancan/model_adapters/mongoid_adapter.rb
+++ b/lib/cancan/model_adapters/mongoid_adapter.rb
@@ -62,7 +62,7 @@ def simplify_relations(model_class, conditions)
             if (relation = model_relations[k])
               relation_class_name = relation[:class_name].blank? ? k.to_s.classify : relation[:class_name]
               v = simplify_relations(relation_class_name.constantize, v)
-              relation_ids = relation_class_name.constantize.where(v).only(:id).map(&:id)
+              relation_ids = relation_class_name.constantize.where(v).distinct(:_id)
               k = "#{k}_id"
               v = { '$in' => relation_ids }
             end
diff --git a/lib/cancan/version.rb b/lib/cancan/version.rb
index 43042322..79171d34 100644
--- a/lib/cancan/version.rb
+++ b/lib/cancan/version.rb
@@ -1,3 +1,3 @@
 module CanCan
-  VERSION = '1.16.0'.freeze
+  VERSION = '1.17.0'.freeze
 end