task_for_pid error 5

I'm trying to use task_for_pid in a project but I keep getting error code 5 signaling some kind of signing error. Even with this script I cant seem to get it to work.

#include <mach/mach_types.h>
#include <stdlib.h>
#include <mach/mach.h>
#include <mach/mach_error.h>
#include <mach/mach_traps.h>
#include <stdio.h>

int main(int argc, const char * argv[]) {
  task_t task;
  pid_t pid = argc >= 2 ? atoi(argv[1]) : 1;
  kern_return_t error = task_for_pid(mach_task_self(), pid, &task);
  printf("%d -> %x [%d - %s]\n", pid, task, error, mach_error_string(error));
  return error;
}

I've tried signing my executables using codesign and also tried building with Xcode with the "Debugging Tool" box checked under hardened runtime. My Info.plist file includes the SecTaskAccess key with the values "allowed" and "debug." Hoping someone can point me towards what I'm missing here. Thanks!