fs寄存器怎么用？怎么编译失败了？

[水墨风光]

我的汇编代码里面这个
mov eax, DWORD PTR FS:[30h]

编译错误提示

error A2108: use of register assumed to ERROR

怎么回事啊？

全部代码：

;#mode = exe

.386
.model flat, stdcall
option casemap :none

;头文件

include windows.inc
include kernel32.inc
include user32.inc

;库文件
includelib kernel32.lib
includelib user32.lib


.data

.data?

.code

start:
xor eax, eax
mov eax, DWORD PTR FS:[30h]
invoke ExitProcess, 0

end start

[killbug2004]

我的方法使用fs前assume fs:nothing

assume fs:nothing
    mov eax, DWORD ptr fs:[30h]

[水墨风光]

调试通过，谢谢啊