I implement a class hierarchy using STI pattern

class A
  scope :aaa, where([someField]:[someValue])
end

class B < A
end

The problem is that when I try to call something like:

B.limit(5).aaa
=> SELECT "[table]".* FROM "[table]" WHERE "[table]"."type" IN ('A') AND ([someField] = [someValue]) LIMIT 5

So I am getting 5 objects of type A, which satisfies scope :aaa But I need to do the same with rows where type = "B"

Is there any way to use scopes from parent, without redifinning it in childs in STI pattern?

Thanks in advance

EDITED

I just discussed it with my frind and he showed me one important thing. A in not the root class of STI. IN fact whole hierarchy looks like

class O < ActiveRecord::Base
end

class A < O
  scope ..... .....
end

class B < A
end

maybe the reason is in hierarchy itself?...