diff --git a/bip-0070.mediawiki b/bip-0070.mediawiki
index 3e861db2..0bf10e22 100644
--- a/bip-0070.mediawiki
+++ b/bip-0070.mediawiki
@@ -221,10 +221,11 @@ used.
 
 Each certificate is a DER [ITU.X690.1994] PKIX certificate value. The
 certificate containing the public key of the entity that digitally
-signed the PaymentRequest must be the first certificate. This MAY be
+signed the PaymentRequest must be the first certificate. This MUST be
 followed by additional certificates, with each subsequent certificate
-being the one used to certify the previous one, up to a trusted root
-authority.  The recipient must verify the certificate chain according to
+being the one used to certify the previous one, up to (but not
+including) a trusted root authority. The trusted root authority MAY be
+included. The recipient must verify the certificate chain according to
 [RFC5280] and reject the PaymentRequest if any validation failure
 occurs.