diff --git a/book/source/17-zoom_certificates.md b/book/source/17-zoom_certificates.md
index ba6f8ab..3bdffa5 100644
--- a/book/source/17-zoom_certificates.md
+++ b/book/source/17-zoom_certificates.md
@@ -645,7 +645,7 @@ User ID Packet, new CTB, 2 header bytes + 19 bytes
     00000010  2e 6f 72 67 3e
 ```
 
-- `CTB: 0xcd`: This is the Packet Type ID for this packet. Bits 7 and 6 show that the packet is in “OpenPGP packet format” (not “Legacy packet format”). The remaining 6 bits encode the type ID’s value: “13,” which is the value for a [User ID packet](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-user-id-packet-tag-13).
+- `CTB: 0xcd`: This is the packet type ID for this packet. Bits 7 and 6 show that the packet is in “OpenPGP packet format” (not “Legacy packet format”). The remaining 6 bits encode the type ID’s value: “13,” which is the value for a [User ID packet](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-user-id-packet-tag-13).
 
 - `length: 0x13`: This field shows the remaining length of the packet (here: 19 bytes).