diff --git a/doc/security-guide/ch024_authentication.xml b/doc/security-guide/ch024_authentication.xml
index d9aa23a324..b227d74641 100644
--- a/doc/security-guide/ch024_authentication.xml
+++ b/doc/security-guide/ch024_authentication.xml
@@ -150,7 +150,7 @@
                 "name": "demo"
             }
         }</screen>
-      <para>Note that the token is often passed within the structure of a larger context of a Identity Service response. These responses also provide a catalog of the various OpenStack services. Each service is listed with its name, access endpoints for internal, admin, and public access.</para>
+      <para>Note that the token is often passed within the structure of a larger context of an Identity Service response. These responses also provide a catalog of the various OpenStack services. Each service is listed with its name, access endpoints for internal, admin, and public access.</para>
       <para>The Identity Service supports token revocation. This manifests as an API to revoke a token, to list revoked tokens and individual OpenStack services that cache tokens to query for the revoked tokens and remove them from their cache and append the same to their list of cached revoked tokens.</para>
     </section>
     <section xml:id="ch024_authentication-idp287584">