diff --git a/conventions.md b/conventions.md
index c331f98..7dc9c90 100644
--- a/conventions.md
+++ b/conventions.md
@@ -172,8 +172,11 @@ value can be represented as `<undefined>`.
 Dates, times, moments, and timestamps can be represented with a
 `Record` with label `rfc3339` having a single field, a `String`, which
 *MUST* conform to one of the `full-date`, `partial-time`, `full-time`,
-or `date-time` productions of
-[section 5.6 of RFC 3339](https://tools.ietf.org/html/rfc3339#section-5.6).
+or `date-time` productions of [section 5.6 of RFC
+3339](https://tools.ietf.org/html/rfc3339#section-5.6). (In
+`date-time`, "T" and "Z" *MUST* be upper-case and "T" *MUST* be used;
+a space separating the `full-date` and `full-time` *MUST NOT* be
+used.)
 
 ## XML Infoset