diff --git a/lib/cancan/ability.rb b/lib/cancan/ability.rb
index 5f86877..2b597e1 100644
--- a/lib/cancan/ability.rb
+++ b/lib/cancan/ability.rb
@@ -228,6 +228,13 @@ module CanCan
       relevant_rules(action, subject).any?(&:only_raw_sql?)
     end
 
+    def merge(ability)
+      ability.send(:rules).each do |rule|
+        rules << rule.dup
+      end
+      self
+    end
+
     private
 
     def unauthorized_message_keys(action, subject)
diff --git a/spec/cancan/ability_spec.rb b/spec/cancan/ability_spec.rb
index 48b6782..3551cce 100644
--- a/spec/cancan/ability_spec.rb
+++ b/spec/cancan/ability_spec.rb
@@ -416,4 +416,17 @@ describe CanCan::Ability do
       @ability.unauthorized_message(:edit, 1..3).should == "edit range"
     end
   end
+
+  describe "#merge" do
+    it "should add the rules from the given ability" do
+      @ability.can :use, :tools
+      another_ability = Object.new
+      another_ability.extend(CanCan::Ability)
+      another_ability.can :use, :search
+
+      @ability.merge(another_ability)
+      @ability.can?(:use, :search).should be_true
+      @ability.send(:rules).size.should == 2
+    end
+  end
 end