Map/Reduce on user classes does not work in JBoss AS

If I execute a MapReduce Task in AS7 a ClassCastEx occurs in the Mapper.

Thanks for help.

~Sandro

java.lang.ClassCastException: org.infinispan.marshall.MarshalledValue cannot be cast to de.adorsys.fireonec2.server.PrimeStats
de.adorsys.fireonec2.server.PrimeCountMapper.map(PrimeCountMapper.java:10)
org.infinispan.commands.read.MapReduceCommand.perform(MapReduceCommand.java:144)
org.infinispan.distexec.mapreduce.MapReduceTask.execute(MapReduceTask.java:285)
org.infinispan.distexec.mapreduce.MapReduceTask.execute(MapReduceTask.java:358)
de.adorsys.fireonec2.server.StatsService.map(StatsService.java:44)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.jboss.as.ee.component.ManagedReferenceMethodInterceptorFactory$ManagedReferenceMethodInterceptor.processInvocation(ManagedReferenceMethodInterceptorFactory.java:72)
org.jboss.invocation.InterceptorContext.proceed(InterceptorContext.java:288)
org.jboss.invocation.InterceptorContext$Invocation.proceed(InterceptorContext.java:374)
org.jboss.as.weld.ejb.Jsr299BindingsInterceptor.doMethodInterception(Jsr299BindingsIntercep