Can't update to MIUI V5 :( Lt18i

[Zaid Waseem]

Hey, I own a xperia arc s . My current MIUI version is 3.2.2 ICS, which I downloaded from MIUI.us . Now I want to update to JB 3.3.29. (Lt18i) from miuiandroid.com. I have downloaded the zip and flashed the given kernel. but while flashing I get an error regarding : assert(getprop("ro.product.device") == "anzu" ||
getprop("ro.build.product")
Please Help!!