diff --git a/java/org/slub/rosetta/dps/repository/plugin/ValidationCatalogResolver.java b/java/org/slub/rosetta/dps/repository/plugin/ValidationCatalogResolver.java
index 9dfa1e147b012842b06e607923981c7aeb27f67b..1f9f008facab9fa5895d4831a3726662e083fc65 100644
--- a/java/org/slub/rosetta/dps/repository/plugin/ValidationCatalogResolver.java
+++ b/java/org/slub/rosetta/dps/repository/plugin/ValidationCatalogResolver.java
@@ -14,7 +14,7 @@ import java.util.List;
 
 class ValidationCatalogResolver implements CatalogResolver {
     private final String[] catalogs;
-    private List<String> errors;
+    private final List<String> errors;
     ValidationCatalogResolver(String[] catalogs, List<String> errors) {
         this.catalogs = catalogs;
         this.errors = errors;