Deserialization error: java.io.InvalidClassException: org.drools.base.evaluators.StrEvaluatorDefinition$StrEvaluator; no valid constructor

java.io.InvalidClassException: org.drools.base.evaluators.StrEvaluatorDefinition$StrEvaluator; org.drools.base.evaluators.StrEvaluatorDefinition$StrEvaluator; no valid constructor 

    private void saveOutput(KnowledgeBuilder kbuilder) throws IOException {
        Collection<KnowledgePackage> kpkgs = kbuilder.getKnowledgePackages();
        String outputFilename = outputFile == null ? "" : outputFile.trim();
        if (outputFilename.isEmpty()) {
            outputFilename = project.getBasedir() + "target/classes/drools.drlx";
        }
        ObjectOutputStream out = null;
        try {
            getLog().info("Saving compiled Drools output to " + outputFilename);
            out = new ObjectOutputStream(new FileOutputStream(outputFilename));
            out.writeObject(kpkgs);
        } finally {
            if (out != null) {
                out.close();
            }
        }
    }

    private Collection<KnowledgePackage> deserializeKnowledgePackages(Resource[] knowledgePackageObjects) throws IOException, ClassNotFoundException {
        Collection<KnowledgePackage> knowledgePackages = new ArrayList<KnowledgePackage>();
        for (Resource knowledgePackageObject : knowledgePackageObjects) {
            LOG.info("Deserializing pre-compiled package " + knowledgePackageObject.getFilename());
            ObjectInputStream in = null;
            try {
                in = new ObjectInputStream(knowledgePackageObject.getInputStream());
                // The input stream might contain an individual package or a collection.
                knowledgePackages.addAll((Collection<KnowledgePackage>) in.readObject());
            } finally {
                if (in != null) {
                    in.close();
                }
            }
        }
        return knowledgePackages;
    }