HTTP Headers not sent when using the browser's back/forward buttons

I am building an add-on that is trying to read the HTTP headers of resources loaded in a browser tab. With the browser.webRequest API, I can do this easily in most situations, except when the browser’s back or forward buttons are used.

None of the browser.webRequest events are triggered when the back or forward buttons are pressed. Since these resources are already in the browser cache, I presume firefox simply loads them from the cache without replaying the headers.

Is there any other way to access these headers when the forward or back buttons are used? I guess the extension can maintain a cache of URLs with its corresponding HTTP headers, but I would like to avoid maintaining this cache since the browser already does this.

Thanks in advance!