v2.4.0-3.0.0 ignore unmanagedClasspath

I have this build.sbt:
https://github.com/ngocdaothanh/xitrum-new/blob/master/build.sbt

which declares unmanagedClasspath like this:

unmanagedClasspath in Compile <+= (baseDirectory) map { bd => Attributed.blank(bd / "config") }

unmanagedClasspath in Runtime <+= (baseDirectory) map { bd => Attributed.blank(bd / "config") }

I want the config directory to be in classpath.

With v2.3.0, .classpath looks like this:

<classpath>
  <classpathentry kind="src" path="src/main/scala" output="target/scala-2.10/classes"/>
  <classpathentry kind="src" path="src/main/java" output="target/scala-2.10/classes"/>
  <classpathentry kind="src" path="src/test/scala" output="target/scala-2.10/test-classes"/>
  <classpathentry kind="src" path="src/test/java" output="target/scala-2.10/test-classes"/>
  <classpathentry kind="lib" path="./config"/>
  <classpathentry kind="lib" path="/Users/ngocdt/.ivy2/cache/org.scala-lang/scala-compiler/jars/scala-compiler-2.10.3.jar"/>
  <classpathentry kind="lib" path="/Users/ngocdt/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.10.3.jar"/>
  <classpathentry kind="lib" path="/Users/ngocdt/.ivy2/cache/org.scala-lang/scala-reflect/jars/scala-reflect-2.10.3.jar"/>
...

But with v2.4.0 and the current 2.5.0-SNAPSHOT, there's no line:

<classpathentry kind="lib" path="./config"/>

You can reproduce the problem:

git clone https://github.com/ngocdaothanh/xitrum-new.git
cd xitrum-new
sbt/sbt eclipse
cat .classpath

Start with the linked xitrum-new build.sbt and reproduce the result using sbt/sbt eclipse, then inspect the generated .classpath. Compare the v2.3.0 output with v2.4.0 and 2.5.0-SNAPSHOT; done means the config directory is represented as a classpath entry again.