diff --git a/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/GraphData.java b/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/GraphData.java
index 8ec1a6e..2ac0e5d 100644
--- a/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/GraphData.java
+++ b/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/GraphData.java
@@ -37,7 +37,7 @@ public class GraphData implements Serializable {
 	private Number maxY = 50000;
 
 	@SuppressWarnings("unused")
-	private GraphData() {
+	public GraphData() {
 		// for serialization issues only
 	}
 
diff --git a/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/Point.java b/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/Point.java
index 485c6b3..b073502 100644
--- a/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/Point.java
+++ b/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/Point.java
@@ -55,7 +55,7 @@ public class Point<S extends Number, T extends Number> implements Serializable {
 	private List<ValueEntry<T>> entries = new Vector<ValueEntry<T>>();
 
 	@SuppressWarnings("unused")
-	private Point() {
+	public Point() {
 		// for serialization only
 	}
 
diff --git a/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/ValueEntry.java b/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/ValueEntry.java
index d507044..727c87e 100644
--- a/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/ValueEntry.java
+++ b/src/main/java/org/gcube/portlets/user/timeseries/charts/support/types/ValueEntry.java
@@ -37,7 +37,7 @@ public class ValueEntry<T extends Number> implements Serializable {
 	private T value = null;
 
 	@SuppressWarnings("unused")
-	private ValueEntry() {
+	public ValueEntry() {
 		// for serialization only
 	}