diff --git a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/oa/provision/model/JoinedEntity.java b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/oa/provision/model/JoinedEntity.java
index da3915aee..a0692cb34 100644
--- a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/oa/provision/model/JoinedEntity.java
+++ b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/oa/provision/model/JoinedEntity.java
@@ -5,14 +5,12 @@ import java.io.Serializable;
 import java.util.LinkedList;
 import java.util.List;
 
-import com.fasterxml.jackson.annotation.JsonSubTypes;
-import com.fasterxml.jackson.annotation.JsonTypeInfo;
-
-import eu.dnetlib.dhp.schema.common.EntityType;
 import eu.dnetlib.dhp.schema.oaf.*;
 
 public class JoinedEntity implements Serializable {
 
+	private static final long serialVersionUID = -6337458773099581114L;
+
 	private OafEntity entity;
 
 	private List<RelatedEntityWrapper> links;