diff --git a/book/source/08-signing_components.md b/book/source/08-signing_components.md
index e3d0ace..9e41e4e 100644
--- a/book/source/08-signing_components.md
+++ b/book/source/08-signing_components.md
@@ -155,12 +155,12 @@ Linking a User ID to an OpenPGP certificate
 
 This signature is calculated over the primary key, User ID and the metadata of the signature packet.
 
-
-### Adding metadata to the primary key
+(primary-metadata)=
+### Adding metadata to the primary key/certificate
 
 The signatures that bind subkeys and identity components to a certificate serve two different purposes: Linking components to the certificate and adding metadata to a component.
 
-The primary key in a certificate doesn't need to be linked to the certificate. It acts as the anchor for linking, itself and thus doesn't require being linked. However, there is nevertheless a need to associate metadata with the primary key.
+The primary key in a certificate doesn't need to be linked to the certificate. It acts as the anchor for linking, itself and thus doesn't require being linked. However, there is nevertheless a need to associate metadata with the primary key, which typically applies to the certificate as a whole.
 
 There are two mechanisms for adding metadata to the primary key: