The documentation for Parcel#readParcelable(ClassLoader) (and its variations) says that you can pass in null to pick up the default class loader. However, that ClassLoader is a system class loader and is not able to find classes in your own application. If you are writing your own classes into the Parcel (not just SDK classes like String and so on), then you should supply a ClassLoader for your application instead; a simple way to obtain one is to just call getClass().getClassLoader() from your own class. http://developer.android.com/reference/android/os/Parcel.html This issue currently affects: FormatParam.java