diff --git a/draft-ietf-privacypass-protocol.md b/draft-ietf-privacypass-protocol.md
index 22937347..a72f78b9 100644
--- a/draft-ietf-privacypass-protocol.md
+++ b/draft-ietf-privacypass-protocol.md
@@ -702,7 +702,7 @@ $ cat spki.bin | xxd -r -p | openssl asn1parse -dump -inform DER
    67:d=1  hl=4 l= 271 prim: BIT STRING
 ~~~
 
-Since Clients truncate `token_key_id` in each `TokenRequest`, Issuers should
+Since Clients truncate `token_key_id` in each `TokenRequest`, Issuers SHOULD
 ensure that the truncated form of new key IDs do not collide with other
 truncated key IDs in rotation.