IPv4 is not getting configured on Ubuntu in a dualstack (IPv4/IPv6) network

I set up a router with IPv6 capabilities (I replaced the firmware with OpenWRT) as my main router and successfully configured DHCP including static leases. Almost everything works fine, all IPv6 capable devices get IPv6 and IPv4 addresses, except when I reboot the router, then my main machine running 14.04 only gets an IPv6 address, which is an issue because my WAN connection is still IPv4 only (and I'm not using a tunnel broker while testing).

Here are screenshots of the corresponding network connection:

Yes, I feel that asking this is naive and pretty embarrassing.

Please correct me if I'm wrong or if there is a better or more user-friendlier way to configure networking with dualstack IPv4/IPv6 on Ubuntu.

Apparently checking the Require IPv4 addressing for this connection to complete does what I wanted: Try to configure both protocols and ensure that an IPv4 is configured for the host, don't just stop the configuration process after IPv6 is configured.

I'm not sure if it was the (german) translation of the option or me just being ignorant and searching in the wrong places for a solution or the possible cause.