diff --git a/src/main/java/org/gcube/documentstore/persistence/PersistenceCouchDB.java b/src/main/java/org/gcube/documentstore/persistence/PersistenceCouchDB.java
index e2785a2..c83b318 100644
--- a/src/main/java/org/gcube/documentstore/persistence/PersistenceCouchDB.java
+++ b/src/main/java/org/gcube/documentstore/persistence/PersistenceCouchDB.java
@@ -74,8 +74,8 @@ public class PersistenceCouchDB extends PersistenceBackend {
 	protected static Record jsonNodeToUsageRecord(JsonNode jsonNode) throws Exception {
 		ObjectMapper mapper = new ObjectMapper();
 		@SuppressWarnings("unchecked")
-		Map<String, Comparable<? extends Serializable>> result = mapper.convertValue(jsonNode, Map.class);
-		Record record =RecordUtility.getRecord(result);
+		Map<String, Serializable> result = mapper.convertValue(jsonNode, Map.class);
+		Record record = RecordUtility.getRecord(result);
 		return record;
 	}