Google App Engine JDO Issue

Question

I am trying to make the following class persistent, but get an UnexpectedException. I have omitted the latter portion of the class.

package com.bingehopper.server;
import java.util.Date;

import javax.jdo.annotations.IdGeneratorStrategy;
import javax.jdo.annotations.IdentityType;
import javax.jdo.annotations.PersistenceCapable;
import javax.jdo.annotations.Persistent;
import javax.jdo.annotations.PrimaryKey;

import com.bingehopper.client.VenueDetails;
import com.google.appengine.api.users.User;

@PersistenceCapable(identityType = IdentityType.APPLICATION)
public class Venue {

  @PrimaryKey
  @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
  private Long id;
  @Persistent
  private User user;
  @Persistent
  private VenueDetails venue;
  @Persistent
  private Date createDate;

  public Venue()
  {

      this.createDate = new Date();

  }

  public Venue(User user, VenueDetails venue)
  {

      this();
      this.user = user;
      this.venue = venue;

  }
}

Here is the error log:

com.google.appengine.tools.development.ApiProxyLocalImpl log
SEVERE: javax.servlet.ServletContext log: Exception while dispatching incoming RPC call
com.google.gwt.user.server.rpc.UnexpectedException: Service method 'public abstract void      com.bingehopper.client.VenueService.addVenue(com.bingehopper.client.VenueDetails) throws com.bingehopper.client.NotLoggedInException' threw an unexpected exception: java.lang.IllegalArgumentException: venue: com.bingehopper.client.VenueDetails is not a supported property type

.

VenueDetails is a class I created in my client package. Can I not use a VenueDetails object variable in my Venue class if I would like it to persist? Or is there a way to make it work? I have no prior experience with GWT and am not sure if I am approaching this the right way. Thank you for your help.