Hi All, my question would be the following: There is a class called DroolsStreamUtils, which is used throughout the drools core library in order to read in contents of a knowledge package from an input stream. The class has the following method: public static Object streamIn(InputStream in, ClassLoader classLoader, boolean compressed) throws IOException, ClassNotFoundException { if (compressed) in = new GZIPInputStream(in); return new DroolsObjectInputStream(in).readObject(); } It creates a DroolsObjectInputStream to read in the object, but it does not uses the specified class loader to create DroolsObjectInputStream instance. The DroolsObjectInputStream is created the with the folloing constructor: public DroolsObjectInputStream(InputStream inputStream) throws IOException { this( inputStream, null ); } public DroolsObjectInputStream(InputStream inputStream, ClassLoader classLoader) throws IOException { super( inputStream ); if ( classLoader == null ) { classLoader = Thread.currentThread().getContextClassLoader(); if ( classLoader == null ) { classLoader = getClass().getClassLoader(); } } this.classLoader = classLoader; this.parentClassLoader = classLoader; } Why can I specify a ClassLoader for DroolsStreamUtils if it is not used? This causes us the following problem: We are using Drools in a web application. We are planning to use Guvnor as our rule repository. We have loaded the rules into the repository and trying to use a KnowledgeAgent with a changeset xml to obtain the package built by Guvnor. When the KnowledgeAgent is trying to build the KnowlegeBase, it fails with a ClassCastException, as it does not find the drools libraries on the class path. The KnowledgeAgent uses the above written DroolsStreamUtils to read in the package contents, and it uses a wrong class loader. The same problem occurs if I am trying to use a KnowledgeBuilder to register the package: . knowledgeBuilder.add(ResourceFactory.newUrlResource("http://localhost:8080/drools-guvnor/org.drools.guvnor.Guvnor/package/com.ii4sm.core.drools.validation/LATEST"), ResourceType.PKG); I can specify a ClassLoader for the KnowledgeBuilder, however it has no effect, since the following code is used by the KnowledgeBuilder to register the package: if ( ResourceType.PKG.equals( type )) { InputStream is = resource.getInputStream(); Package pkg = (Package) DroolsStreamUtils.streamIn( is ); is.close(); addPackage( pkg ); } As the DroolsStreamUtils won't use the class loader specified for the KnowledgeBuilder, this approach fails as well. If I read in the package with my own code, creating a DroolsObjectInputStream with the correct class loader, everything works fine. Am I doing something wrong? Cheers, Szabolcs