diff --git a/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/MergeUtils.java b/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/MergeUtils.java
index f1221add3..7606a4d2f 100644
--- a/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/MergeUtils.java
+++ b/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/MergeUtils.java
@@ -655,6 +655,13 @@ public class MergeUtils {
 			return d1;
 		}
 
+		if (StringUtils.contains(d1.getValue(), "null")) {
+			return d2;
+		}
+		if (StringUtils.contains(d2.getValue(), "null")) {
+			return d1;
+		}
+
 		return Stream
 			.of(d1, d2)
 			.min(