  TOI-1227 b is an 11 Myr old validated transiting planet in the middle of its
contraction phase, with a current radius of 0.85 R$_J$. It orbits a low-mass
pre-main sequence star (0.170 M$_\odot$, 0.56 R$_\odot$) every 27.4 days. The
magnetic activity of its young host star induces radial velocity jitter and
prevents good measurements of the planetary mass. We gathered additional
transit observations of TOI-1227 b with space- and ground-based telescopes, and
we detected highly significant transit-timing variations (TTVs). Their
amplitude is about 40 minutes and their dominant timescale is longer than 3.7
years. Their most probable origin is dynamical interactions with additional
planets in the system. We modeled the TTVs with inner and outer perturbers near
first and second order resonances; several orbital configurations provide an
acceptable fit. More data are needed to determine the actual orbital
configuration and eventually measure the planetary masses. These TTVs and an
updated transit chromaticity analysis reinforce the evidence that TOI-1227 b is
a planet.
