Can't log in while f.lux is adjusting the screen

[alexdi]

On a late-2013 rMBP with the most current version of El Capitan, I can't type anything at the login screen while the screen color is changing. This occurs when I use the system during the day, let it sleep, then open the lid in the evening. The screen begins to change color at the password screen. All keypresses are recorded and deferred until the animation finishes, at which point, if I've correctly entered my password and hit Enter, the system logs in.

The delay is annoying. How can I fix this? Thanks.