GWT 2.4 ValidationTool fails on a Date property on a ValueProxy

I was looking around the web for a couple of hours now, but I did not find any hints on this. I'm currently in progress of learning GWT (started with 2.4.0), and I'm setting up a RequestFactory. Everything went good until the point I ran the annotation processor.

Here is the relevant proxy class:

@ProxyFor(value = PlaylistModel.class)
public interface PlaylistProxy extends ValueProxy {

    Long getPlaylistId();

    String getPlaylistName();

    void setPlaylistName(String playlistName);

    Date getPlaylistStartTime();

    void setPlaylistStartTime(Date playlistStartTime);
}

But the annotation processor gives me the following error:

error: Could not find domain method similar to java.util.Date getPlaylistStartTime()
error: Could not find domain method similar to void setPlaylistStartTime(java.util.Date)

For me it seems that the problem is caused by the java.util.Date return value and parameter, although the official documentation tells that this type is a transportable type.

The type which will be proxied is:

public class PlaylistModel implements Serializable {

    private static final long serialVersionUID = 7476233813742570809L;

    private Long playlistId;

    @NotNull
    @Size(min = 1)
    private String playlistName;

    private Date playlistStartDate;

    private ChannelModel channel;

    public Long getPlaylistId() {
        return playlistId;
    }

    public void setPlaylistId(final Long playlistId) {
        this.playlistId = playlistId;
    }

    public String getPlaylistName() {
        return playlistName;
    }

    public void setPlaylistName(final String playlistName) {
        this.playlistName = playlistName;
    }

    public Date getPlaylistStartDate() {
        return playlistStartDate;
    }

    public void setPlaylistStartDate(final Date playlistStartDate) {
        this.playlistStartDate = playlistStartDate;
    }

    public ChannelModel getChannel() {
        return channel;
    }

    public void setChannel(final ChannelModel channel) {
        this.channel = channel;
    }
}

Could anyone please point me to the right direction?

getPlaylistStartTime vs. getPlaylistStartDate