Safari cached "Failed to open page"

Page I'm working with, accessible only via VPN. My VPN connection drops when MacBook goes to sleep, and on wake it reconnects to VPN. But during this 5 seconds delay, Safari can't open this page, as VPN connection isn't connected yet, so Safari tells that the page isn't available. After successful connection, Safari still can't open the page. However, Chrome can open it and other browsers too.

I tried to empty cache, but it didn't help. Clearing all history isn't a good solution, as a lot of data is stored there and I don't want to loose it.

Does someone know how to fix this bug?

I was able to fix this annoying behavior with flushing local DNS cache:

sudo killall -HUP mDNSResponder