Scala compiler breaks groovy module

I'm working on a multi-module project. Some modules are scala based and some java & groovy. The groovy modules depend on scala & java modules. Hence intellij sets the scala module for the groovy project. And then that breaks the compilation as the scala compiler fails to find groovy base classes

scala: error: cannot find symbol

scala:extends ...A groovy base class..

If I remove the scala facet I get the same errors as the scala compiler still compiles the groovy project.

Any ideas what's going on?