OpenMP crash with derived type

I am using Fortran Compiler XE 15.0.1.148 .

When I compile and run the following simple program in Debug mode, it runs fine without any errors or warnings.  However, it crashes if I compile it in optimized Release mode.  I can prevent it from crashing if I disable the /Qopenmp option.  My guess is that the problem has something to do with having a derived type variable declared as private in OpenMP loop.

program test_derived_type
implicit none

type T
   integer,allocatable:: a(:)
end type T

type(T):: b
integer i, s

s = 0

!$OMP parallel do default(none), schedule(dynamic), &
!$OMP&         private(i,b), reduction(+:s)
do i = 1, 100
   print*, i

   allocate( b%a(i) )
   b%a = 1

   s = s + sum(b%a)

   deallocate(b%a)
end do  ! i
!$OMP end parallel do

write(*,*) 's =', s
stop
end program test_derived_type