Infinispan cannot put inner classes to write-behind cache

final class PojoCoder implements Serializable {
    private static final long serialVersionUID = -6238699065180988597L;

    private String name_;
    private String favouriteLanguage_;

    PojoCoder(String name, String favouriteLanguage) {
        name_ = name;
        favouriteLanguage_ = favouriteLanguage;
    }

    @Override
    public String toString() {
        return name_ + " loves " + favouriteLanguage_;
    }

    public String getFavouriteLanguage() {
        return favouriteLanguage_;
    }

    public String getName() {
        return name_;
    }
}

final EmbeddedCacheManager cacheManager = new DefaultCacheManager();
        cacheManager.defineConfiguration(CACHE_NAME,
                new ConfigurationBuilder()
                        .eviction()
                        .maxEntries(2)

                        .persistence()
                        .passivation(false)
                        .addSingleFileStore()
                        .location(tmpStoragePath)
                        .maxEntries(6)

                        .build());

final Cache<String, PojoCoder> testCache = cacheManager.getCache(CACHE_NAME);
testCache.put("alex", new PojoCoder("django-lover alex", "Python")); //NotSerializableException on this line