How do I prevent my cd ripper from overwriting Unknown Album when metadata can't be found

I'm starting the longish process of ripping my CD collection. I've got abcde installed with the config from Andrew's Corner . It seems to be working ok but when the metadata fetch fails, the MP3s get written as Unknown Artist and Unknown Album. Which isn't a problem until the second metadata fetch fails. Then the tracks get overwritten. What would be ideal is that the second album gets a number on the name like "Unknown Album 2". Any suggestions on how to accomplish this? Or how to keep the directories from being ovewritten?