diff --git a/dmp-backend/elastic/src/main/java/eu/eudat/elastic/repository/DmpRepository.java b/dmp-backend/elastic/src/main/java/eu/eudat/elastic/repository/DmpRepository.java
index 4acfea5f6..4d2a9cc90 100644
--- a/dmp-backend/elastic/src/main/java/eu/eudat/elastic/repository/DmpRepository.java
+++ b/dmp-backend/elastic/src/main/java/eu/eudat/elastic/repository/DmpRepository.java
@@ -174,7 +174,7 @@ public class DmpRepository extends ElasticRepository<Dmp, DmpCriteria> {
 		}
 
 		if (criteria.getCollaborators() != null && criteria.getCollaborators().size() > 0) {
-			boolQuery = boolQuery.should(QueryBuilders.termsQuery(Dmp.MapKey.COLLABORATORS.getName() + ".id.keyword", criteria.getCollaborators().stream().map(UUID::toString).collect(Collectors.toList())));
+			boolQuery = boolQuery.should(QueryBuilders.termsQuery(Dmp.MapKey.COLLABORATORS.getName() + ".id.keyword", criteria.getCollaborators().stream().filter(Objects::nonNull).map(UUID::toString).collect(Collectors.toList())));
 		}
 
 		if (!criteria.isAllowAllVersions()) {