  Let $k$ be a complete non-Archimedean field, $L$ a finite tamely ramified
galoisian extension of $k$ and $X$ a $k$-analytic space. We show that $X$ is
isomorphic to a closed $k$-polydisc (resp. a $k$-lace) if and only if $X_L$ is
isomorphic to a closed $L$-polydisc (resp. a $L$-lace) on which the action of
$\mathrm{Gal}(L/k)$ is reasonable.
