Angular read array from ActivatedRoute params

I am observing what looks like an inconsistent format when reading ActivatedRoute params.

• when the component is first reached with an array of parameters in the url (localhost:1/a;t=1,2), params['t'] comes out as a string: '1,2'
• when navigating programmatically via the router later, the same kind of url is produced (localhost:1/a;t=1,2), but now params['t'] is an array of numbers [1, 2]

In both cases the params are obtained via the same subscription, done at init:

constructor(private router: Router, private route: ActivatedRoute) {}

ngOnInit() {
  this.route.params.subscribe((params: Params) => {
      console.info(JSON.stringify(params)),
  });
}

// if needs be, here's how I perform the programmatic navigation
this.router.navigate(['.', {t:[1,2]}], {relativeTo: this.route})

Of course I can check the type of the params I get and convert before using, but it seems a bit ugly. Is this something known or am I missing something ?