Failing instead of completing build activities - possible?

Hi,
I want to use build activities to delineate my build, however I've noticed that build activities don't fail as I expect them to.

Imagine I have a build with a target as follows (I've already tried this)

<startBuildActivity label="Get file" autocomplete="true" ... />
<fail message="testing" />
<startBuildActivity label="Process file" autocomplete="true" ... />

The build obviously fails, but the build activity "Get file" is marked as complete even though a failure occurred before the next <startBuildActivity> or the end of the build script when it's automatically completed?

In this scenario I want the build activity to be marked as failed so I can easily pinpoint whereabouts in the build a failure has occurred.

This seems like a fairly normal request so have I missed something, as from looking around, at the API too, there doesn't seem to be a way to mark a build activity as failed, only completed!

Thanks in advance.