Cannot both create and activate venv in zsh

[qsantos]

~% mkdir a
~% cd a
~/a% slap venv -c -a
creating local environment "3.10" (using python3)
warning: the -a,--activate option only works when shadowed by a shell function
source "/Users/quentin.santos/a/.venvs/3.10/bin/activate"
  1.92s user 0.41s system 67% cpu 3.473 total
~/a% slap venv -a
activating local environment "3.10"