Marshalling a java.util.Date in Serializable throws: DateNotActiveException: Fields were never written

Marshalling the following class:

static class TestSerializable000 implements Serializable {
public String contentType;
public byte[] data;
public Date lastModified = new Date();

public TestSerializable000() {}

public TestSerializable000(String contentType, byte[] data)

{ this.contentType = contentType; this.data = data; }

}

Fails with:

java.io.NotActiveException: Fields were never written
at org.jboss.marshalling.river.RiverObjectOutputStream.finish(RiverObjectOutputStream.java:174)
at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1075)
at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:955)
at org.jboss.marshalling.river.RiverMarshaller.doWriteFields(RiverMarshaller.java:1129)
at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1085)
at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:955)
at org.jboss.marshalling.AbstractMarshaller.writeObject(AbstractMarshaller.java:407)
at org.jboss.test.marshalling.SimpleMarshallerTests$51.runWrite(SimpleMarshallerTests.java:1705)
at org.jboss.test.marshalling.TestBase.runReadWriteTest(TestBase.java:109)
at org.jboss.test.marshalling.SimpleMarshallerTests.testSerializable000(SimpleMarshallerTests.java:1703)
Caused by: an exception which occurred:
in field lastModified
in object org.jboss.test.marshalling.SimpleMarshallerTests$TestSerializable000@b041b0
... Removed 22 stack frames