[NTG-context] hyphenation question

In a document where \mainlanguage[fr] some words weren't hyphenated correctly so I've put them in a hyphenation pattern \hyphenation{ ap-pa-ren-ce at-ten-dai-ent com-men-cent d'am-bi-tion d'in-flu-en-ce l'ap-pa-ren-ce } The only ones who still don't get hyphenated corresponding to the above pattern are those with d'..., l'... Porqué ? Alan