diff --git a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/ResourceManagerAdapter.java b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/ResourceManagerAdapter.java
index 752dbbcde2..2bc2193561 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/ResourceManagerAdapter.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/ResourceManagerAdapter.java
@@ -45,6 +45,9 @@ class ResourceManagerAdapter<MODEL_OBJECT extends ModelObject, DTO extends HalRe
    */
   public Response update(String id, Function<MODEL_OBJECT, MODEL_OBJECT> applyChanges) {
     MODEL_OBJECT existingModelObject = manager.get(id);
+    if (existingModelObject == null) {
+      return Response.status(Response.Status.NOT_FOUND).build();
+    }
     MODEL_OBJECT changedModelObject = applyChanges.apply(existingModelObject);
     return update(id, changedModelObject);
   }