Updating actualWork via fusion

We are attempting to update the "Actual Hours" on a task via Fusion. I seem to be able to update virtually everything about the task except the Actual Hours field.  

We are mapping to "actualWork" which is not marked as read only in the documentation but when my scenarios run, there are no errors, but the "actual hours" field does not change.

Does anyone know if it is tied to another field that also needs to be updated?  We have attempted to update the field with Fusion's built in integration and through an API call, but it is the same result either way.