Where is the error in this update with join

update snx_comuni set sta_id = 2782
from snx_comuni
inner join snx_province on snx_comuni.provincia_id =
snx_province.provincia_id
inner join snx_regioni on snx_province.regione_id = snx_regioni.regione_id
where snx_regioni.codice_regione = 'PIE'