Apple today released an updated version of OS X 10.9.1 for developers, which has a build number of 13B40



From MacRumors:

Today's release comes nearly two weeks after the second 10.9.1 beta, which had a build number of 13B35. Last week?s build included several fixes for Gmail in OS X Mail, along with improvements to the Smart Mailbox functionality. It also included bug fixes for emojis when used with VoiceOver, and included an update to the Shared Links tab when the Safari Sidebar is open. Build 13B40 includes the same fixes.

  Apple Seeds OS X 10.9.1 Build 13B40 to Developers