Certificate error is not triggered on Windows

I can reproduce this with the following simple, python based https server: https://gist.github.com/dergachev/7028596

Steps to reproduce:

1. Download simple-https-server.py
2. Generate custom certificate: openssl req -new -x509 -keyout server.pem -out server.pem -days 365 -nodes
3. Start server: python simple-https-server.py
4. Start simplebrowser and navigate to https://localhost:4443

Expected Result:
Certificate error dialog pops up due to untrusted certificate

Actual Result:
ERR_CONNECTION_REFUSED error page

Notes

• Chrome works as expected on the same machine
• 5.10.1 and 5.11.0 beta4 sometimes works
• Custom built 5.11 always fails but sometimes with timeout
• Always works as expected on Linux