diff --git a/erc/ERCS/erc-4337.md b/erc/ERCS/erc-4337.md
index ef3f571e..e237b73b 100644
--- a/erc/ERCS/erc-4337.md
+++ b/erc/ERCS/erc-4337.md
@@ -678,9 +678,16 @@ Still, it might require putting a "semi-valid" signature (e.g. a signature in th
 
 ##### Error Codes:
 
-Same as `eth_sendUserOperation`
+Same as `eth_sendUserOperation`, with additions.
+
 This operation may also return an error if the inner call to the account contract reverts.
 
+Additional codes:
+
+  * **code: -32521** - execution reverted during account call
+    * The `message` field MAY contain a revert message, if the call reverted with a message.
+    * The `data` field MAY contain the revert bytes, if the call reverted with contract specific bytes.
+
 #### * eth_getUserOperationByHash
 
 Return a UserOperation based on a hash (userOpHash) returned by `eth_sendUserOperation`