When a module (B) is included into another module (M) before that module is included into another class (A), everything works fine and the methods of the second module (B) are accessible. However if it is included after the original module (M) was included in the class (A), the method is not known.

breaks.rb

module M
end

module B
  def a
    puts 'wuhuuu'
  end
end

class A
  include M
end

M.send(:include, B)

A.new.a # raises no method error

works_fine.rb

module M
end

module B
  def a
    puts 'wuhuuu'
  end
end

M.send(:include, B)

class A
  include M
end

A.new.a # works fine (wuhuuu)

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