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 e29ec9d19..7681fa76f 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
@@ -2,13 +2,14 @@
 package eu.dnetlib.dhp.oa.provision.model;
 
 import java.io.Serializable;
+import java.util.ArrayList;
 import java.util.List;
 
 public class JoinedEntity implements Serializable {
 
 	private TypedRow entity;
 
-	private List<Tuple2> links;
+	private List<Tuple2> links = new ArrayList<>();
 
 	public JoinedEntity() {
 	}