diff --git a/canonical-binary.md b/canonical-binary.md
index 9542c50..9ae6b60 100644
--- a/canonical-binary.md
+++ b/canonical-binary.md
@@ -57,7 +57,10 @@ following the total order relation defined in the
 **Dictionaries.**
 The key-value pairs in a `Dictionary` MUST be serialized sorted in
 ascending order by key, following the total order relation defined in
-the [Preserves specification][spec].
+the [Preserves specification][spec].[^no-need-for-by-value]
+
+  [^no-need-for-by-value]: There is no need to order by (key, value)
+    pair, since a `Dictionary` has no duplicate keys.
 
 **Other kinds of `Value`.**
 There are no special canonicalization restrictions on `String`s,