Bug with 64-bit dword registers in proc64.inc / fastcall?

Hi, I'm getting "Error: operand sizes do not match" on this line of code:

Code:

invoke  wsprintf, rdi, msg, r12d

I also tried adding the dword size modifier, but still get the error:

Code:

invoke  wsprintf, rdi, msg, dword r12d

The fastcall macro translates the last parameter to "mov r8b, r12d":

Code:

        else if size@param = 1
         if ~ param eq r8b
          mov r8b,param
         end if
        end if

I then tracked it down to where size@param was being set:

Code:

        virtual
         origin = $
         inc param
         load opcode byte from origin
         if opcode = 67h; | opcode = 41h
          load opcode byte from origin+1
         end if
         if opcode and 0F8h = 48h
          size@param = 8
         else if opcode = 66h
          size@param = 2
         else if opcode = 0FFh
          size@param = 4
         else
          size@param = 1
         end if
        end virtual

The commented-out part is my addition to fix the problem. For some reason, the "inc r12d" instruction in this case gets encoded with the 0x41 prefix-opcode added to it.