System Information
Operating system: Windows 10
Graphics card: GeForce GTX 1080 Ti

Blender Version
Broken:
2.80, 8ba86020cc50, blender2.8, 2019-01-16
)

Short description of error
When using the Defocus node in the compositor, the z-depth does not adjust when rendering animation.

Exact steps for others to reproduce the error
Focus on a cube (in camera settings), then set very low f-stop (so only a sliver of the cube is in focus) in the defocus node. Animate the cube's position. Render a few frames as stills to confirm that node is functioning properly. When I Render Animation, the focus does not move to follow cube; it focuses on the first frame, then loses focus afterwards.