Is a non-Muslim maternal uncle through rada'ah (nursing) considered a lawful mahram to my wife?

The suckling of a disbelieving woman establishes حرمة (prohibition) just like that of a Muslim woman. So, if a man and the wife's mother were suckled by the same woman, the man becomes the wife's maternal uncle through suckling. However, the degree of محرمية (unmarriageability) with a disbeliever differs from that with a Muslim. It is not permissible to travel with him, and being in seclusion with him may be prohibited, especially with a Zoroastrian, due to a lack of trustworthiness. The suckling that establishes prohibition is five full sucklings.