diff --git a/18.md b/18.md
index 9d0ce1c6..c8bf224c 100644
--- a/18.md
+++ b/18.md
@@ -43,3 +43,6 @@ Quote reposts MUST include the bech32-encoded `nevent`, `note`, or `naddr` of th
 event in the content. The embedded entity should match the type of the tag (in
 other words, if embedding a `naddr`, the `q` tag should contain an address, not
 an event id).
+
+Quote reposts also SHOULD include a `k` tag matching the stringified `kind` of
+the quoted note.