diff --git a/security-notes/OSSN-0047 b/security-notes/OSSN-0047
index 553e809f..bfda4b48 100644
--- a/security-notes/OSSN-0047
+++ b/security-notes/OSSN-0047
@@ -86,7 +86,7 @@ that contains the certificate of the identity provider is specific to
 each 'Location' directive.  This configuration will not allow a signed
 assertion from 'idp1' to be used against the authentication URL for
 'idp2'.  An attempt to do so would be rejected by mod_auth_mellon and
-would never actually reach Keystone's OS-FEDERATION extention.
+would never actually reach Keystone's OS-FEDERATION extension.
 
 It is recommended to read the Keystone federation documentation as well
 as the documentation for the HTTPD module that you are using for your