Battery Isolator

[Jaguarjack]

I have bought one of those isolators that you undo the wheel to break the circuit for my Mazda because it has an alarm fitted that drains the battery if it's not used for a week or so.
I duly fitted it to the negative terminal as instructed , however when I undo the contact wheel the alarm goes off !
If I disconnect the positive terminal first , it's fine
My question is can I fit the isolator to the positive instead with no adverse results ?