diff --git a/spec.md b/spec.md
index 762a94636..4f155c6e6 100644
--- a/spec.md
+++ b/spec.md
@@ -136,6 +136,11 @@ a stand-alone event format and stored in the message body.
 A "binary-mode message" is one where the event data is stored in the message
 body, and event attributes are stored as part of message meta-data.
 
+Regardless of which mode is used, protocol bindings MAY choose to provide
+additional formatting and structure to the message body. For example, a
+wrapper around the event might be used, or several events could be batched
+together into a single message.
+
 #### Protocol
 
 Messages can be delivered through various industry standard protocol (e.g. HTTP,