NPE (fatal) when compiling DRL declare...extends generic type

import java.util.Set;
declare Person extends Set
name : String
end

Compiling crashes with

Exception in thread "main" java.lang.NullPointerException
at org.drools.compiler.PackageBuilder.mergeInheritedFields(PackageBuilder.java:1173)
at org.drools.compiler.PackageBuilder.processTypeDeclarations(PackageBuilder.java:1267)
at org.drools.compiler.PackageBuilder.mergePackage(PackageBuilder.java:932)
at org.drools.compiler.PackageBuilder.newPackage(PackageBuilder.java:920)
at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:631)
at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:310)
at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:486)
at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:28)

This is related to 3040 but is NOT remedied by changing (restricting) the syntax.