diff --git a/lib/cancan/can_definition.rb b/lib/cancan/can_definition.rb
index 7cb56f1..718ad38 100644
--- a/lib/cancan/can_definition.rb
+++ b/lib/cancan/can_definition.rb
@@ -68,7 +68,11 @@ module CanCan
     end
 
     def matches_subject?(subject)
-      @subjects.include?(:all) || @subjects.include?(subject) || @subjects.any? { |sub| sub.kind_of?(Class) && subject.kind_of?(sub) }
+      @subjects.include?(:all) || @subjects.include?(subject) || matches_subject_class?(subject)
+    end
+
+    def matches_subject_class?(subject)
+      @subjects.any? { |sub| sub.kind_of?(Class) && (subject.kind_of?(sub) || subject.kind_of?(Class) && subject.ancestors.include?(sub)) }
     end
 
     def matches_conditions_hash?(subject, conditions = @conditions)
diff --git a/spec/cancan/ability_spec.rb b/spec/cancan/ability_spec.rb
index d070c65..1402e59 100644
--- a/spec/cancan/ability_spec.rb
+++ b/spec/cancan/ability_spec.rb
@@ -135,6 +135,13 @@ describe CanCan::Ability do
     @ability.can?(:read, :nonstats).should be_false
   end
 
+  it "should check ancestors of class" do
+    @ability.can :read, Numeric
+    @ability.can?(:read, Integer).should be_true
+    @ability.can?(:read, 1.23).should be_true
+    @ability.can?(:read, "foo").should be_false
+  end
+
   it "should support 'cannot' method to define what user cannot do" do
     @ability.can :read, :all
     @ability.cannot :read, Integer