  The most recent SH0ES measurement of the Hubble constant, based on type Ia
supernovae from the Pantheon+ compilation, employs corrections of supernova
peak magnitudes which effectively accounts for extinction in the supernova host
galaxies. These corrections are estimated using a probabilistic model which is
trained on Hubble flow (z>0.03) supernovae and extrapolated to the calibration
galaxies (those with observed Cepheid distances). By comparing the corrected
peak magnitudes to distance moduli from Cepheids, we show that this standard
approach underestimates the brightness of reddened supernovae in the high
stellar-mass ($M_{\star}>10^{10}M_{\odot}$) calibration galaxies. This can be
traced back to the fact that for these galaxies, a low total-to-selective
extinction coefficient (R_B~3) is assumed, while for the low stellar-mass
analogues a more standard R_B~4 is assumed. We propose a minimalistic
modification of the Pantheon+ extinction model in order to alleviate this
systematic effect. The modification is twofold and it involves: (i) the same,
Milky Way-like distribution of R_B in all calibration galaxies (with mean R_B
of 4.3 -- consistent with the extinction curve used for colour corrections of
the Cepheids -- and scatter 0.4) and (ii) a modified shape of the E(B-V)
reddening distribution while keeping the same effective slope of the supernova
peak magnitude-colour relation and the same mean E(B-V) reddening as measured
for supernovae in the Hubble flow. We show that this new approach yields a
significantly better fit ($\Delta$BIC=-11) to the calibration data and results
in a lower value of the derived Hubble constant through a stronger extinction
correction of supernovae in the calibration galaxies. Our result is
$H_{0}=70.5\pm1$ km/s/Mpc implying a reduction of the tension with the Planck
$H_{0}$ measurement assuming a flat LCDM cosmology from $5.2\sigma$ to
$2.8\sigma$.
