If 2 libraries share the same package name, this is now a build breakage, unless all libraries share the same package. This is because the libraries R classes only contain the resources declared in the libraries themselves (plus dependencies). Since two libraries could share the same package name without depending on one another, it's possible to ensure that creating only one R class would work for both. (Merging both R class might be possible but is too risky for a quick fix like this). If all the libraries share the same package, then a single R class is created for that package that contains all the symbol of the app (simpler than merging all the symbols for now) If a library and the app share the same package name, the R class for the library is not created (since the R class for the app contains all resources). This already worked in ADT, so this changeset only fixes Ant. Change-Id: I95f0b734ba263051961268d960d59749f5b6e1a5