beforeNavigate event is not firing on the next page after Top Sites

Question

So I've got this code in my extension's background script:

safari.application.addEventListener("beforeNavigate", function(event) {
    console.log(event.url);
}, true);

After I've opened the new tab with Top Sites, background console is showing me the following:

null

Seems right, but when I'm trying to navigate from this page to next one, using address bar, console shows nothing.

Breakpoint, in the background script, isn't hit also.

Does anyone had the same problem?

Thanks in advance.