KeyError: 'void' when trying to build interface with f2py

[Zweigstelle]

Hi again @jameskermode
I tried to use f90wrap with a very simple test implementation.

module simple_module 
  use, intrinsic :: iso_fortran_env, only: REAL64, INT32
  type, public :: simple_type
    integer(kind=INT32) :: a 
    real(kind=REAL64) :: b 
    contains 
      !Setter subroutines
      !Getter functions
      !Finalize routines
  end type simple_type
  contains
  ! Definitions of Routines and Functions
end module simple_module

I defined the kind_map file containing

{
  'integer' : {'INT32' : 'int', '4' : 'int'}, 
  'real' : {'REAL64': 'double', '8' : 'double'} 
}

f90wrap -k kind_map -m simple simple_module.f90

produces the file f90wrap_simple_module.f90 and simple.py.
If I then try to run

f2py -c -m _simple f90wrap_simple_module.f90 

I end up with

Building modules...
        Building module "_simple"...
                Constructing wrapper function "f90wrap_simple_type_initialise"...
                  this = f90wrap_simple_type_initialise()
                Constructing wrapper function "f90wrap_simple_type_finalise"...
                  f90wrap_simple_type_finalise(this)
                Constructing wrapper function "f90wrap_set_a"...
getctype: No C-type found in "{}", assuming void.
getctype: No C-type found in "{}", assuming void.
getctype: No C-type found in "{}", assuming void.
Traceback (most recent call last):
 #Lot of Traceback output
... line 416, in getpydocsign
    sig = '%s : %s %s%s' % (a, opt, c2py_map[ctype], init)

KeyError: 'void'

I'm probably missing something, but I could not find anything in the docs which resolved my issue.
Thanks in advance and best regards