Later, on the basis of the treaty of commerce between France and Japan, Petitjean was permitted to build a church for French residents on a hill overlooking Nishizaka in Nagasaki (the martyrdom square of twenty-six saints of Japan).
後にプティジャンは日仏通商条約にもとづいて長崎の西坂（日本二十六聖人の殉教地）を見ることができる丘の上に居留地に住むフランス人の為に教会を建築する許可を得た。