Hi there, I am having problems adding knowledge packages to a kb. For instance I create a kb n' add this drl: package test rule "abc" then System.out.println("abc"); end then I want to add another drl with the same package. package test rule "123" then System.out.println("123"); end this is the code i'm using for adding public static void add(KnowledgeBase kb, String content) throws Exception { (1) KnowledgeBuilder builder = KnowledgeBuilderFactory.newKnowledgeBuilder(kb); (2) builder.add( ResourceFactory.newByteArrayResource(content.getBytes()), ResourceType.DRL); if (builder.hasErrors()) throw new Exception(builder.getErrors().toString()); kb.addKnowledgePackages(builder.getKnowledgePackages()); } please notice i am creating a new builder every time and the kb is passed in on (1) the first call to add works fine. but on the second i get a NullPointerException on line (2) java.lang.NullPointerException at org.drools.rule.builder.dialect.java.PackageStore.write(PackageStore.java:47) at org.drools.commons.jci.compilers.EclipseJavaCompiler$3.acceptResult(EclipseJavaCompiler.java:350) at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:474) at org.drools.commons.jci.compilers.EclipseJavaCompiler.compile(EclipseJavaCompiler.java:358) at org.drools.commons.jci.compilers.AbstractJavaCompiler.compile(AbstractJavaCompiler.java:49) at org.drools.rule.builder.dialect.java.JavaDialect.compileAll(JavaDialect.java:369) at org.drools.compiler.DialectCompiletimeRegistry.compileAll(DialectCompiletimeRegistry.java:53) at org.drools.compiler.PackageRegistry.compileAll(PackageRegistry.java:71) at org.drools.compiler.PackageBuilder.compileAll(PackageBuilder.java:869) at org.drools.compiler.PackageBuilder.addPackage(PackageBuilder.java:826) at org.drools.compiler.PackageBuilder.addPackageFromDrl(PackageBuilder.java:404) at org.drools.compiler.PackageBuilder.addKnowledgeResource(PackageBuilder.java:586) at org.drools.builder.impl.KnowledgeBuilderImpl.add(KnowledgeBuilderImpl.java:37) thank you very much mike