[sbt] forking tests in scalatest and bootclasspath

Hi,

I have a problem with forking tests in scalatest (but judging from the
code, the problem might be in other frameworks as well). I have a custom
scala compiler which is correctly set in the build file and picked up
during the compilation.
I also have some simple tests written without any help of the popular
frameworks (simple execution of main). In those tests I create a new
instance of the compiler and run it on some files. For that to work I have
to have 'fork in run := true' (or in Test for scalatest to work).
Now, I tried to port those tests to scalatest and everything is great until
I try to run them when I get the usual:
"scala.reflect.internal.MissingRequirementError: object scala.runtime in
compiler mirror not found."

which suggests that my custom scala jars weren't put on the bootclasspath.
I had a quick look into testing/src/main/scala and I don't see that
distinction being made there (classpath vs bootclasspath) but then I am not
so familiar with that part of the codebase.

Any help would be appreciated.

Thanks,
hubert