error: using (__attribute(__at()))

I'm using the uvision and I want to define a variable at a specific address.

I figured out that it should work like

int main(void)
{
  int var __attribute__((__at(0x40001000))) = 20;
}

but I always get the error message "expected an attribute name".

www.keil.com/.../armccref_ch04s05s02.htm

best regards
Alan Scott