Cache fails to update due to missing ETAG header field

Hi, thanks for this library. :)

I am currently implementing a web scraper, which utilizes it and have come across the following issue:
The web server i am contacting does not seem to provide a ETAG Header (https://www.koblenz.de/rathaus/verwaltung/pressemeldungen/).
The initial caching worked and i was happy. But then the content of the website got updated and my scraper never got the new content, as cached_path seems to think, that the cached content is still up to date.

Can you confirm this behavior or might this be something i did wrong?

Edit: I am using version 0.5.1