Docker appears to bind containers to IPv6 ports instead of IPv4 ports

Issue

• When port-binding with containers, docker seems to bind containers to IPv6 ports instead of IPv4 ports.
• I have disabled IPv6 via sysctls, but netstat still shows docker binding to IPv6, for example:

# netstat -tulpen | grep docker
tcp6       0      0 :::80                   :::*                    LISTEN      0          112062     76761/docker-proxy
tcp6       0      0 :::8080                 :::*                    LISTEN      0          113272     76737/docker-proxy
tcp6       0      0 :::443                  :::*                    LISTEN      0          113295     76753/docker-proxy
tcp6       0      0 :::8443                 :::*                    LISTEN      0          112043     76745/docker-proxy