Retrofit EOF Error

@POST("/announcements")
Announcement insertAnnouncement(
        @Body Announcement announcement,
        @Query("auth") String authToken
);

public class Announcement implements Serializable {
    public String module_id;
    public String user_id;

    public String title;
    public String description;

    public int timestamp;

    public Announcement(String module_id, String user_id, String title, String description) {
        this.module_id = module_id;
        this.user_id = user_id;

        this.title = title;
        this.description = description;

        this.timestamp = 0;
    }
}