CY, take a look at the teshuvah, and for good measure, I’ll throw in a link to a discussion I had with cherrybim about it (turned out, I was wrong, and he was right).
http://hebrewbooks.org/pdfpager.aspx?req=920&pgnum=94
http://www.theyeshivaworld.com/coffeeroom/topic/kosher-switch/page/2#post-565940