HAR includes requests from the local cache

[soulgalore]

If I access a page, and then do another access for the same URL, assets that are from the cache is in the HAR:

The first request has wrong response code (it should be a 304, it is a 200). The length of the timings are 0 if they are fetched from the cache. The cache field in the HAR is empty.

Do you know if this is something wrong in the trigger or is the problem in Firefox?