Overloaded operator for derived type undefined when imported from a wrapper module

The following code does not compile with Intel Fortran v16, v17, on x86-64 Linux:

module mymod
implicit none

type :: mytype
  private
  integer :: a
  contains
  procedure,private :: eq
  generic :: operator(==) => eq
endtype mytype

interface mytype
  module procedure :: constructor
endinterface mytype

contains

type(mytype) function constructor(a)
  integer,intent(in),optional :: a
  if(present(a))then
    constructor % a = a
  else
    constructor % a = 0
  endif
endfunction constructor

logical function eq(m0,m1)
  class(mytype),intent(in) :: m0
  class(mytype),intent(in) :: m1
  eq = m0 % a == m1 % a
endfunction eq

endmodule mymod

module wrapper_module
use mymod,only:mytype
endmodule wrapper_module

program test
use wrapper_module
implicit none

write(*,*)mytype() == mytype(0)

endprogram test

The compiler does not seem to resolve the overloaded == operator for mytype:

$ ifort test.f90
test.f90(44): error #6355: This binary operation is invalid for this data type.
write(*,*)mytype() == mytype(0)
----------^
test.f90(44): error #6355: This binary operation is invalid for this data type.
write(*,*)mytype() == mytype(0)
----------------------^
compilation aborted for test.f90 (code 1)

If the main program accesses mytype directly from mymod, the program compiles and executes as expected.

If the main program accesses mytype from wrapper_module, and wrapper module accesses mytype via "use mymod", the program compiles and executes as expected.

If the main program accesses mytype from wrapper_module, and wrapper module accesses mytype via "use mymod,only:mytype" (the example code above), the compilation fails with the above message. I think this is unexpected behavior.

The code compiles and executes as expected when compiled with gfortran 5.x

Thanks,

milan