operand

Why is this an invalid operand?

I have the following ASM file generated by a compiler I'm writing: ; This code has been generated by the 7Basic ; compiler <http://launchpad.net/7basic&gt; ; Uninitialized data SECTION .bss v_0 resb 4 v_4 resb 4 v_8 resb 4 ; Code SECTION .text push 1 pop eax mov v_0, eax push 2 pop eax mov v_4, eax mov eax, v_0 push eax ...