diff --git a/lib/Qpsmtpd/SMTP.pm b/lib/Qpsmtpd/SMTP.pm
index be4184c..01f54a7 100644
--- a/lib/Qpsmtpd/SMTP.pm
+++ b/lib/Qpsmtpd/SMTP.pm
@@ -322,7 +322,7 @@ sub auth_parse_respond {
         return $self->{_auth} = Qpsmtpd::Auth::SASL($self, $mechanism, @stuff);
     }
 
-    $self->respond(504, "Unimplemented authentification mechanism: $mechanism");
+    $self->respond(504, "Unimplemented authentication mechanism: $mechanism");
     return DENY;
 }