  The angular coverage extension of the KLOE-2 electromagnetic calorimeter,
from a polar angle of 20$^{\circ}$ down to $8^{\circ}$, will increase the
multiphoton detection capability of the experiment enhancing the search reach
for rare kaon, $\eta$ and $\eta'$ prompt decay channels. The basic layout of
the calorimeter extension consists of two small barrels of LYSO crystals
readout with APD photosensors aiming to achieve a timing resolution between 300
and 500 ps for 20 MeV photons. The first test of a (5.5$\times6\times$13)
cm$^3$ prototype for such a detector was carried out in april 2009 at the Beam
Test Facility of Laboratori Nazionali di Frascati of INFN with an electron beam
from 100 to 500 MeV. In the selected energy range, we measured a light yield of
500$\div$800 p.e./Mev, an energy resolution which can be parametrized as $0.05
\oplus 0.01/({\rm E/GeV}) \oplus 0.015/\sqrt{\rm{E/GeV}}$, a position
resolution of 2.8 mm and a timing resolution of 200$\div$300 ps.
