diff --git a/lib/cancan/model_adapters/mongoid_adapter.rb b/lib/cancan/model_adapters/mongoid_adapter.rb
index fb45c86..7993252 100644
--- a/lib/cancan/model_adapters/mongoid_adapter.rb
+++ b/lib/cancan/model_adapters/mongoid_adapter.rb
@@ -23,18 +23,22 @@ module CanCan
       end
 
       def database_records
-        if @rules.size == 0  
+        if @rules.size == 0
           @model_class.where(:_id => {'$exists' => false, '$type' => 7}) # return no records in Mongoid
         elsif @rules.size == 1 && @rules[0].conditions.is_a?(Mongoid::Criteria)
           @rules[0].conditions
         else
-          @rules.inject(@model_class.all) do |records, rule|
-            if rule.conditions.empty?
-              records
-            elsif rule.base_behavior
-              records.or(rule.conditions)
+          # we only need to process can rules if
+          # there are no rules with empty conditions
+          rules = @rules.reject { |rule| rule.conditions.empty? }
+          process_can_rules = @rules.count == rules.count
+          rules.inject(@model_class.all) do |records, rule|
+            if process_can_rules && rule.base_behavior
+              records.or rule.conditions
+            elsif !rule.base_behavior
+              records.excludes rule.conditions
             else
-              records.excludes(rule.conditions)
+              records
             end
           end
         end
diff --git a/spec/cancan/model_adapters/mongoid_adapter_spec.rb b/spec/cancan/model_adapters/mongoid_adapter_spec.rb
index 175a846..1ce0466 100644
--- a/spec/cancan/model_adapters/mongoid_adapter_spec.rb
+++ b/spec/cancan/model_adapters/mongoid_adapter_spec.rb
@@ -68,6 +68,15 @@ if ENV["MODEL_ADAPTER"] == "mongoid"
         MongoidProject.accessible_by(@ability, :read).entries.should == [sir]
       end
 
+      it "should be able to mix empty conditions and hashes" do
+        @ability.can :read, MongoidProject
+        @ability.can :read, MongoidProject, :title => 'Sir'
+        sir  = MongoidProject.create(:title => 'Sir')
+        lord = MongoidProject.create(:title => 'Lord')
+
+        MongoidProject.accessible_by(@ability, :read).count.should == 2
+      end
+
       it "should return everything when the defined ability is manage all" do
         @ability.can :manage, :all
         sir   = MongoidProject.create(:title => 'Sir')