diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java
index 0026ee9aa..845c4c982 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java
@@ -323,13 +323,13 @@ public class Result extends OafEntity implements Serializable {
 		if (a.size() == b.size()) {
 			int msa = a
 				.stream()
-				.filter(i -> i.getValue() != null)
+				.filter(i -> i != null && i.getValue() != null)
 				.map(i -> i.getValue().length())
 				.max(Comparator.naturalOrder())
 				.orElse(0);
 			int msb = b
 				.stream()
-				.filter(i -> i.getValue() != null)
+				.filter(i -> i != null && i.getValue() != null)
 				.map(i -> i.getValue().length())
 				.max(Comparator.naturalOrder())
 				.orElse(0);