With indifferent access returns Hash on transformation methods (ruby 2.5.1)

[arturictus]

When calling compact returns a Hash instead of indifferent_access

irb(main):001:0> h = Fusu::HashWithIndifferentAccess.new({hello: 'hello'})
=> {"hello"=>"hello"}
irb(main):002:0> h_c = h.compact
=> {"hello"=>"hello"}
irb(main):003:0> h_c.class
=> Hash
irb(main):004:0> h_c.fetch(:hello)
Traceback (most recent call last):
        3: from bin/console:14:in `<main>'
        2: from (irb):4
        1: from (irb):4:in `fetch'
KeyError (key not found: :hello)