Flashing TK GApps

So I'm running PAC ROM; I have a slight issue, I want stock GApps on my phone to add some features I've been wanting. When I flash it (tk_gapps-stock-5.1.1-20150809-signed.zip) on the official Nexus 5 lolipop ROM I got an error message, I read it and it says that I need to flash is ontop of another TK GApps, unless I wipe my cashe partition. So I wiped my Davlick Cashe and Cashe. Still have me the same message. Did I read it wrong? Any tips? Thanks