As I was going through Parashat Behalotecha, I noticed that the word "Cushit", referring to Moshe's wife, is spelled two different ways in the same pasuk, once with a chaf and once with a khaf. Does anyone know why this might be? Do any sources attach any special significance to this? NB I am aware of the term's meaning in modern Hebrew, please don't bring that up unless it's relevant to your answer.
וַתְּדַבֵּ֨ר מִרְיָ֤ם וְאַהֲרֹן֙ בְּמֹשֶׁ֔ה עַל־אֹד֛וֹת הָאִשָּׁ֥ה הַכֻּשִׁ֖ית אֲשֶׁ֣ר לָקָ֑ח כִּֽי־אִשָּׁ֥ה כֻשִׁ֖ית לָקָֽח׃
Miriam and Aaron spoke against Moses because of the Cushite woman he had married: “He married a Cushite woman!”