diff --git a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/RepositoryPermissionDtoToRepositoryPermissionMapper.java b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/RepositoryPermissionDtoToRepositoryPermissionMapper.java
index 43efb19c07..8e015e8b60 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/RepositoryPermissionDtoToRepositoryPermissionMapper.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/RepositoryPermissionDtoToRepositoryPermissionMapper.java
@@ -1,10 +1,11 @@
 package sonia.scm.api.v2.resources;
 
+import org.mapstruct.CollectionMappingStrategy;
 import org.mapstruct.Mapper;
 import org.mapstruct.MappingTarget;
 import sonia.scm.repository.RepositoryPermission;
 
-@Mapper
+@Mapper(collectionMappingStrategy = CollectionMappingStrategy.TARGET_IMMUTABLE)
 public abstract class RepositoryPermissionDtoToRepositoryPermissionMapper {
 
   public abstract RepositoryPermission map(RepositoryPermissionDto permissionDto);