diff --git a/src/main/java/eu/dnetlib/repo/manager/service/AggregationServiceImpl.java b/src/main/java/eu/dnetlib/repo/manager/service/AggregationServiceImpl.java
index 507dc93..e1cbcb3 100644
--- a/src/main/java/eu/dnetlib/repo/manager/service/AggregationServiceImpl.java
+++ b/src/main/java/eu/dnetlib/repo/manager/service/AggregationServiceImpl.java
@@ -67,11 +67,8 @@ public class AggregationServiceImpl implements AggregationService {
 
     private <T extends AggregationInfo> Map<String, List<T>> createYearMap(List<T> aggregationHistory) {
 
-        aggregationHistory = aggregationHistory.stream()
-                .sorted(Comparator.comparing(AggregationInfo::getDate).reversed())
-                .collect(Collectors.toList());
-
         return aggregationHistory.stream()
+                .sorted(Comparator.comparing(AggregationInfo::getDate).reversed())
                 .collect(Collectors.groupingBy(item -> getYear(item.getDate())));
     }