diff --git a/book/source/glossary.md b/book/source/glossary.md
index f95fb15..71fe528 100644
--- a/book/source/glossary.md
+++ b/book/source/glossary.md
@@ -478,7 +478,7 @@ Reason For Revocation Subpacket
     See [RFC 5.2.3.31](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-reason-for-revocation)
 
 Reference Time
-    A point in time at which an {term}`OpenPGP Certificate` is evaluated.
+    A point in time at which an {term}`OpenPGP Certificate` or {term}`OpenPGP Signature` is evaluated.
 
 Regular Expression Subpacket
     An {term}`OpenPGP Signature Subpacket` which allows for limiting {term}`delegations<Delegation>` to {term}`identities<Identity>` matching a regular expression.