diff --git a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/GroupResource.java b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/GroupResource.java
index f8c7a3852c..affdf94332 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/GroupResource.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/GroupResource.java
@@ -87,6 +87,7 @@ public class GroupResource {
   @Consumes(VndMediaType.GROUP)
   @StatusCodes({
     @ResponseCode(code = 204, condition = "update success"),
+    @ResponseCode(code = 400, condition = "Invalid body, e.g. illegal change of id/group name"),
     @ResponseCode(code = 401, condition = "not authenticated / invalid credentials"),
     @ResponseCode(code = 403, condition = "not authorized, the current user does not have the \"group\" privilege"),
     @ResponseCode(code = 404, condition = "not found, no group with the specified id/name available"),
diff --git a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserResource.java b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserResource.java
index f1d9596b3e..2356e81ed7 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserResource.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserResource.java
@@ -93,6 +93,7 @@ public class UserResource {
   @Consumes(VndMediaType.USER)
   @StatusCodes({
     @ResponseCode(code = 204, condition = "update success"),
+    @ResponseCode(code = 400, condition = "Invalid body, e.g. illegal change of id/user name"),
     @ResponseCode(code = 401, condition = "not authenticated / invalid credentials"),
     @ResponseCode(code = 403, condition = "not authorized, the current user does not have the \"user\" privilege"),
     @ResponseCode(code = 404, condition = "not found, no user with the specified id/name available"),