diff --git a/includes/classes/WPCLI/Command/GetSiteStats.php b/includes/classes/WPCLI/Command/GetSiteStats.php
index 758eba0d..6a0314b8 100644
--- a/includes/classes/WPCLI/Command/GetSiteStats.php
+++ b/includes/classes/WPCLI/Command/GetSiteStats.php
@@ -74,6 +74,7 @@ public static function get_args(): array {
 					'name'        => 'clear-cache',
 					'description' => esc_html__( 'Clear the cache before retrieving the stats (can be intensive).', 'accessibility-checker' ),
 					'repeating'   => false,
+					'optional'    => true,
 				],
 			],
 		];