impossible combination of address sizes and invalid effective address on simple operation

Question

I have some assembly, the following lines of which are causing nasm to complain about impossible combination of address sizes and invalid effective address:

mov [rbp], eax
mov [rbp - 4], eax
mov edi, [rbp]
mov esi, [rbp - 4]
mov edi, [rbp - 8]
mov [rbp - 8], eax

Why is this?

Answer 1

Stupid mistake, pointed out by Michal Petch.

Forgot to add the -f macho64 flag (-f elf64 on Linux).