diff --git a/dbrepo-metadata-service/repositories/src/main/java/at/tuwien/mapper/MetadataMapper.java b/dbrepo-metadata-service/repositories/src/main/java/at/tuwien/mapper/MetadataMapper.java
index 74284789247ee20deac7df99c49a4f60e8cfa765..eaef36188bf5d5c832ba30d91b8b62e91b10c646 100644
--- a/dbrepo-metadata-service/repositories/src/main/java/at/tuwien/mapper/MetadataMapper.java
+++ b/dbrepo-metadata-service/repositories/src/main/java/at/tuwien/mapper/MetadataMapper.java
@@ -219,6 +219,9 @@ public interface MetadataMapper {
 
     /* keep */
     default String nameIdentifierSchemeTypeToUri(NameIdentifierSchemeType data) {
+        if (data == null) {
+            return null;
+        }
         switch (data) {
             case ROR -> {
                 return "https://ror.org/";