diff --git a/src/main/java/org/gcube/accounting/datamodel/UsageRecord.java b/src/main/java/org/gcube/accounting/datamodel/UsageRecord.java
index 883bb1b..4c725e7 100644
--- a/src/main/java/org/gcube/accounting/datamodel/UsageRecord.java
+++ b/src/main/java/org/gcube/accounting/datamodel/UsageRecord.java
@@ -9,7 +9,7 @@ import org.gcube.accounting.exception.InvalidValueException;
 
 public interface UsageRecord extends Comparable<UsageRecord> {
 	
-	public enum OperationResult {
+	public enum OperationResult implements Serializable, Comparable<OperationResult> {
 		SUCCESS, FAILED
 	}