itunes won’t allow me to backup my iphone x. It only wants to restore from a backup.

I’ve had my iPhone X (iOS 12) for about 2 months now, and I’m trying trying to do my first backup to iTunes on my Windows 10 pc. iTunes doesn’t give me an option to backup my device. It assumes that this is a brand new device and that I want to do a fresh install from one of my previous iPad backups. This is the first time that I’ve connected this iPhone to iTunes. I can’t get past the restore page. How do I back it up?