diff --git a/lib/cancan/can_definition.rb b/lib/cancan/can_definition.rb
index e9ac0fd..5a4079a 100644
--- a/lib/cancan/can_definition.rb
+++ b/lib/cancan/can_definition.rb
@@ -79,7 +79,8 @@ module CanCan
     private
 
     def subject_class?(subject)
-      (subject.kind_of?(Hash) ? subject.values.first : subject).class == Class
+      klass = (subject.kind_of?(Hash) ? subject.values.first : subject).class
+      klass == Class || klass == Module
     end
 
     def matches_action?(action)
diff --git a/spec/cancan/ability_spec.rb b/spec/cancan/ability_spec.rb
index 9f8886e..951245b 100644
--- a/spec/cancan/ability_spec.rb
+++ b/spec/cancan/ability_spec.rb
@@ -23,6 +23,14 @@ describe CanCan::Ability do
     end
     @ability.can?(:read, :some_symbol).should == true
   end
+  
+  it "should pass nil to a block when no instance is passed" do
+    @ability.can :read, Symbol do |sym|
+      sym.should be_nil
+      true
+    end
+    @ability.can?(:read, Symbol).should be_true
+  end
 
   it "should pass to previous can definition, if block returns false or nil" do
     @ability.can :read, Symbol
@@ -257,6 +265,17 @@ describe CanCan::Ability do
     @ability.can?(:read, A).should be_true
     @ability.can?(:read, A.new).should be_true
   end
+  
+  it "should pass nil to a block for ability on Module when no instance is passed" do
+    module B; end
+    class A; include B; end
+    @ability.can :read, B do |sym|
+      sym.should be_nil
+      true
+    end
+    @ability.can?(:read, B).should be_true
+    @ability.can?(:read, A).should be_true
+  end
 
   it "passing a hash of subjects should check permissions through association" do
     @ability.can :read, Range, :string => {:length => 3}