sbt-imported project: libraryDependencies not seen by Java code

There seems to be a problem with sbt based projects that are purely Java: The `libraryDependencies` are not seen by the compiler. For example:

autoScalaLibrary := false

crossPaths       := false

mainClass := Some("de.sciss.eisenkraut.Main")

libraryDependencies += "de.sciss" % "weblaf" % "1.28"

Here I have some Java source code `Main.java`. Inside I use the WebLaF library, but the package imports and classes of WebLaF are red. In the Project Settings, the library has correctly been created, but the compilation fails:

    Error:(28, 28) java: package com.alee.laf.toolbar does not exist


Best, .hh.