valid operand size but shows warning

[lab-bat]

Using nasm (current master) on following file (command: nasm -fwin32 -w+all test.asm -o test.obj -l test.lst)

section .text
test:
BITS 16
o32     pushf
o32     popf
o32     ret
o32     ret     0
o32     retf
o32     retf    0
o32     iret
BITS 32
o16     pushf
o16     popf
o16     ret
o16     ret     0
o16     retf
o16     retf    0
o16     iret
BITS 64
o16     pushf
o16     popf
o16     ret
o16     ret     0
o16     retf
o16     retf    0
o16     iret
o32     pushf
o32     popf
o32     ret
o32     ret     0
o32     retf
o32     retf    0
o32     iret
.end:

shows the following warning

test.asm:4: warning: invalid operand size prefix o32, must be o16 [-w+prefix-opsize]
test.asm:5: warning: invalid operand size prefix o32, must be o16 [-w+prefix-opsize]
test.asm:10: warning: invalid operand size prefix o32, must be o16 [-w+prefix-opsize]
test.asm:12: warning: invalid operand size prefix o16, must be o32 [-w+prefix-opsize]
test.asm:13: warning: invalid operand size prefix o16, must be o32 [-w+prefix-opsize]
test.asm:18: warning: invalid operand size prefix o16, must be o32 [-w+prefix-opsize]
test.asm:20: warning: invalid operand size prefix o16, must be o64 [-w+prefix-opsize]
test.asm:21: warning: invalid operand size prefix o16, must be o64 [-w+prefix-opsize]
test.asm:26: warning: invalid operand size prefix o16, must be o64 [-w+prefix-opsize]
test.asm:27: warning: invalid operand size prefix o32, must be o64 [-w+prefix-opsize]
test.asm:28: warning: invalid operand size prefix o32, must be o64 [-w+prefix-opsize]
test.asm:33: warning: invalid operand size prefix o32, must be o64 [-w+prefix-opsize]

But those size override prefix is valid. I cannot use -w-prefix-opsize because o16 mov eax, [si] or o32 mov ax, [esi] critical warning would be silented, too.