SOA Error - "Failed to compile bpel generated classes"

When trying to compile an AIA composite project I'm getting the following error:

Error(13,63): Instantiation exception for implementation type "implementation.bpel", validating component "CreateCustomerPartyLAProvABCSImplProcess". Exception is "Failed to compile bpel generated classes.
failure to compile the generated BPEL classes for BPEL process "CreateCustomerPartyLAProvABCSImplProcess" of composite "default/CreateCustomerPartyLAProvABCSImpl!1.0"
The class path setting is incorrect.
Ensure that the class path is set correctly. If this happens on the server side, verify that the custom classes or jars which this BPEL process is depending on are deployed correctly. Also verify that the run time is using the same release/version."

This is because I'm missing a library:

Go to project preference/Library classpath

Add the library aia.jar:

Solved!