After a Location.go(), History.back() does not trigger ActivatedRoute.paramMap

Consider this URL:

http://localhost:4200/items

I use Location.go() to update the URL when an element is opened (expanded) in my GUI:

http://localhost:4200/items;openedId=123

When I hit the back button, the URL is changed back to http://localhost:4200/items, but my subscription on ActivatedRoute.paramMap is not triggered. (and therefore my item is stays opened)

Oddly enough, it is triggered when I open two elements consecutively, and then hit back two times:

Open main page -> http://localhost:4200/items
Open item 123  -> http://localhost:4200/items;openedId=123
Open item 456  -> http://localhost:4200/items;openedId=456

Back to http://localhost:4200/items;openedId=123 -> ActivatedRoute.paramMap triggered
Back to http://localhost:4200/items -> ActivatedRoute.paramMap triggered (!)

Why isnt't it triggered the first time? Why do I need to have two history entries before it works? I am confused.

Update: This is how I listen for changes in the paramMap:

  public ngOnInit() {

    this.subscriptions.add(this.activatedRoute.paramMap.subscribe(paramMap => {
      this.handleNavigation(paramMap);
    }));
}

from After a Location.go(), History.back() does not trigger ActivatedRoute.paramMap