diff --git a/src/message-protocol.adoc b/src/message-protocol.adoc
index 09e693c..40ef24c 100644
--- a/src/message-protocol.adoc
+++ b/src/message-protocol.adoc
@@ -350,5 +350,5 @@ specification or the extension version mismatch.
 
 |
 | < -127
-| _Vendor specific_.
+| _Vendor or Implementation specific_.
 |===