This fails:- *Test * package com.guvnor.tests; import org.drools.compiler.PackageBuilder; import org.drools.compiler.PackageBuilderErrors; import org.drools.io.ResourceFactory; import org.drools.lang.descr.PackageDescr; public class FragmentsTest { public static final void main(String[] args) { try { PackageBuilderErrors pbe; PackageBuilder pb = new PackageBuilder(); pb.addPackage( new PackageDescr( "p3" ) ); pb.addPackageFromDrl( ResourceFactory.newClassPathResource( "Fragment1.drl" ) ); pbe = pb.getErrors(); System.out.println("Errors = " + pbe.getErrors().length ); pb.addPackageFromDrl( ResourceFactory.newClassPathResource( "Fragment2.drl" ) ); pbe = pb.getErrors(); System.out.println("Errors = " + pbe.getErrors().length ); pb.addPackageFromDrl( ResourceFactory.newClassPathResource( "Fragment3.drl" ) ); pbe = pb.getErrors(); System.out.println("Errors = " + pbe.getErrors().length ); pb.getPackage(); } catch ( Exception e ) { e.fillInStackTrace(); e.printStackTrace(); } } } *Fragment1.drl * package com.guvnor.package3 import com.guvnor.package1.Person import java.math.BigDecimal *Fragment2.drl * package com.guvnor.package3 //import com.guvnor.package1.Person <<Fails unless I add this import declare Person end declare Person2 extends Person name : String age : Integer end *Fragment3.drl * package com.guvnor.package3 rule "test" when Person( salary == 10 ) then System.out.println("Hello Fred!"); end Resolved with https://github.com/droolsjbpm/drools/commit/dc00433f3e3821a2c224ba8dc36f0...