  The Vainshtein mechanism is known as an efficient way of screening the fifth
force around a matter source in modified gravity. This has been verified mainly
in highly symmetric matter configurations. To study how the Vainshtein
mechanism works in a less symmetric setup, we numerically solve the scalar
field equation around a disk with a hole at its center in the cubic Galileon
theory. We find, surprisingly, that the Galileon force is enhanced, rather than
suppressed, in the vicinity of the hole. This anti-screening effect is larger
for a thinner, less massive disk with a smaller hole. At this stage our setup
is only of academic interest and its astrophysical consequences are unclear,
but this result implies that the Vainshtein screening mechanism around less
symmetric matter configurations is quite nontrivial.
