diff --git a/book/source/04-certificates.md b/book/source/04-certificates.md
index e0d334f..d0ec862 100644
--- a/book/source/04-certificates.md
+++ b/book/source/04-certificates.md
@@ -112,8 +112,7 @@ The commonly used key flags are:
 
 By convention, only the primary key is allowed to perform "certification" operations. All other operations can be configured on either the primary key or a subkey.
 
-```{admonition} Note
-:class: note
+```{note}
 
 It is considered good practice to have separate component keys for each type of operation: to allow only *Certification* operations with the primary key, and to use separate *Signing*, *Encryption* and *Authentication* subkeys [^key-flag-sharing].
 ```