Apple has seeded the first developer beta of OS X Mavericks 10.9.1. This will be the first incremental update to Mavericks when it ships to the public. Apple has released a fix for Gmail in the Mail app on Mavericks, but the OS remains at version 10.9.
It’s currently unclear when 10.9.1 will be available for everyone, and there are no known issues with this first beta.
Source: Apple