[Cin] Keyframe Adjustments Not Seen in Render

I've added a couple keyframes to adjust the curves in Histogram Bezier at the end of a clip. When I play in the compositor I see the change (lower highlights as I pan into a scene lit by the sun) as expected. When I render, either background rendering or a full render for output, it seems the changes are ignored and the curves don't change with time. Am I missing something? Regards, Mark