diff --git a/preserves.md b/preserves.md
index c30344d..aac4552 100644
--- a/preserves.md
+++ b/preserves.md
@@ -607,7 +607,7 @@ case-by-case basis.
 
 There is *no* ordering requirement on the `E_i` elements or
 `K_i`/`V_i` pairs.[^no-sorting-rationale] They may appear in any
-order. However, the `E_i` and `K_i` must be pairwise distinct.
+order. However, the `E_i` and `K_i` *MUST* be pairwise distinct.
 
   [^no-sorting-rationale]: In the BitTorrent encoding format,
     [bencoding](http://www.bittorrent.org/beps/bep_0003.html#bencoding),