Error with internal subprogram in impure elemental routine

Greetings,

i got an error with the impure feature. It states: error #7949: All internal subprograms in a pure subprogram shall be pure.
It does not matter, wether the routines are functions or subroutines.

module test_mod

contains

  impure elemental subroutine foo()

    contains

    function bar()
      integer :: bar
      bar = 1
    end function

  end subroutine

end module

I wanted to pack some output statements in an internal subroutine to avoid code duplication.
Would this approach be valid?

Wolf