negative pointer addition overflows uintptr

[TotallyGamerJet]

Given this C code:

int main() {
  int *ptr = 0;
  ptr -= 3;
  return 0;
}

Results in this Go Code:

package main

import (
	"os"
	"unsafe"
)

func main() {
	var ptr *int = nil
	ptr = (*int)(unsafe.Add(unsafe.Pointer(ptr), -(unsafe.Sizeof(int(0)) * 3)))
	os.Exit(0)
}

The negative number overflows uintptr from unsafe.Sizeof. Just casting it to any signed number fixes the error. Should it be a cast to int because that is usually the same size as the register like uintptr?