diff --git a/src/main/java/org/gcube/accounting/analytics/ResourceRecordQuery.java b/src/main/java/org/gcube/accounting/analytics/ResourceRecordQuery.java
index cac1fa7..c183975 100644
--- a/src/main/java/org/gcube/accounting/analytics/ResourceRecordQuery.java
+++ b/src/main/java/org/gcube/accounting/analytics/ResourceRecordQuery.java
@@ -40,7 +40,7 @@ public class ResourceRecordQuery {
 	 * Records Types
 	 * @return the Map
 	 */
-	public static Map<Class<? extends SingleUsageRecord>, Set<String>> getResourceRecordsTypes() {
+	public static synchronized Map<Class<? extends SingleUsageRecord>, Set<String>> getResourceRecordsTypes() {
 		if(resourceRecords==null){
 			resourceRecords = new HashMap<Class<? extends SingleUsageRecord>, Set<String>>();
 			Package usageRecordPackage = ServiceUsageRecord.class.getPackage();