diff --git a/aep/general/0151/aep.md.j2 b/aep/general/0151/aep.md.j2
index 42b42d5e..1374331b 100644
--- a/aep/general/0151/aep.md.j2
+++ b/aep/general/0151/aep.md.j2
@@ -75,10 +75,18 @@ but is not obligated to do so:
 
 - Resources that accept multiple parallel requests **may** place them in a
   queue rather than work on the requests simultaneously.
-- Resource that does not permit multiple requests in parallel (denying any new
-  request until the one that is in progress finishes) **must** return
-  `409 Conflict` if a user attempts a parallel request, and include an error
-  message explaining the situation.
+
+{% tab proto %}
+
+- A resource that does not support concurrent mutation requests **must** return an
+  `ABORTED` error if the resource has an outstanding mutation.
+
+{% tab oas %}
+
+- A resource that does not support concurrent mutation requests **must** respond
+  with a `409 Conflict` status code if the resource has an outstanding mutation.
+
+{% endtabs %}
 
 ### Expiration