Would you be offended if someone asked you this?

So I have a really close guy friend who is a year younger than me. We are just friends and nothing more. Well prom is coming up, and I would like to know that I have a back up in case *gulp* no one would ask me.
Would It be bad for me to ask Jacob (my friend) to be my backup in case I don't get asked or is that rude?
P.S. he is a sophomore so it's not like he has the option of asking someone!