Black bars on all sides of screen at 1080p (native res. 1440p)

My monitor's native resolution is 1440p. After overclocking it I decided I wanted to reduce the game resolution to 1080p for higher fps.

At 1080p, the game appears centered on the monitor with black bars filling the rest of the screen. When I set the resolution to any other 16:9 resolution, it scales perfectly to fit the full screen.

Does anyone know how to fix this? I only have this issue dota.

#EDIT: driver was a version behind. the update fixed it ^Thanks ^for ^the ^help ^anyway