diff --git a/_includes/markdown/Design.md b/_includes/markdown/Design.md
index 1628aa94..02920ec0 100644
--- a/_includes/markdown/Design.md
+++ b/_includes/markdown/Design.md
@@ -171,7 +171,7 @@ If a management UI is impossible due to the nature of the project, credentials s
 <?php
 // Production API keys should ideally be defined in wp-config.php
 // This section should default to a development or noop key instead.
-if ( ! defined( 'CLIENT_MANDRILL_API_KEY' ) {
+if ( ! defined( 'CLIENT_MANDRILL_API_KEY' ) ) {
     if ( 'production' === wp_get_environment_type() ) {
         define( 'CLIENT_MANDRILL_API_KEY', '1234567890' );
     }