diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index dc75cf4..b53e461 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -177,7 +177,7 @@ the primary User ID can also specify metadata about the primary key
 While 
 [user attributes](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-user-attribute-packet-tag-1) are similar to User IDs, they are less commonly used.
 
-Currently, the OpenPGP standard prescribes only one format for storing user attributes: an [image](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-the-image-attribute-subpack). Typically, this image represents the key owner, but it is not required.
+Currently, the OpenPGP standard prescribes only one format to be stored in user attributes: an [image](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-the-image-attribute-subpack). Typically, this image represents the key owner, although it is not required.
 
 ## Linking the components