SwiftPackage with Swift and C Targets and external dependency

I created a Package which include Swift and C code, plus dependency to another swift package.

The package builds without problems with DEVELOPMENT-SNAPSHOT-2016-05-31-a.

But it doesn’t build with 3.0-PREVIEW-2.

I get the following error: fatal error: ClangModule ClangModule(SOLPOS) can't have SwiftModule(Strand) as a dependency.: …

When I move the C code in extra Package, it builds again.

But I would like to know if this behaviour is intended or a bug of spm.

You can find the project here:

https://github.com/damuellen/SwiftSolar