Using a pickup with an acoustic guitar in Garageband with a macbook Air; what gives????

I just don't get it.

I have a brand new Macbook Air that came with Garageband 11. I'm trying to use my acoustic pickup to record me playing my acoustic guitar in Garageband and it just won't recognize it. The pickup works just fine when I choose electric guitar, but the pickup isn't recognized under microphone options when I choose acoustic. It will ONLY let me use the built in mic, and seems like it will ONLY recognize a true microphone for recording an acoustic guitar.

Either I'm an idiot (which I'm hoping is the case) or this is a stupid oversight to ONLY allow acoustic guitars to be recorded with a microphone and not a pickup.

Again, I want to be clear: my macbook, the pickup and garageband all work perfectly as I can record using the pickup with my acoustic guitar if I choose electric guitar in garageband. I'm trying to figure out how to use the pickup when choosing an acoustic guitar in garageband.

I thank anyone who can help me.