[ERROR] | update-alternatives: error: alternative g++ can't be slave of gcc: it is a master alternative #1957

➜  ~ cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04.6 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.6 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
➜  ~ sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-10 60 --slave /usr/bin/g++ g++ /usr/bin/g++-10
[sudo] password for danny:
update-alternatives: error: alternative g++ can't be slave of gcc: it is a master alternative