diff --git a/04-onion-routing.md b/04-onion-routing.md
index 30a6352e4..d6c68563d 100644
--- a/04-onion-routing.md
+++ b/04-onion-routing.md
@@ -1057,9 +1057,17 @@ The _erring node_:
 The _origin node_:
   - once the return message has been decrypted:
     - SHOULD store a copy of the message.
-    - SHOULD continue decrypting, until the loop has been repeated 20 times.
+    - SHOULD continue decrypting, until the loop has been repeated 27 times
+    (maximum route length of tlv payload type).
     - SHOULD use constant `ammag` and `um` keys to obfuscate the route length.
 
+### Rationale
+
+The requirements for the _origin node_ should help hide the payment sender.
+By continuing decrypting 27 times (dummy decryption cycles after the error is found)
+the erroring node cannot learn its relative position in the route by performing
+a timing analysis if the sender were to retry the same route multiple times.
+
 ## Failure Messages
 
 The failure message encapsulated in `failuremsg` has an identical format as