diff --git a/src/wp-includes/class-wp-locale.php b/src/wp-includes/class-wp-locale.php
index 0fcb130b81f9d..7416c3e316e0a 100644
--- a/src/wp-includes/class-wp-locale.php
+++ b/src/wp-includes/class-wp-locale.php
@@ -266,7 +266,7 @@ public function init() {
 	 * @return string Full translated weekday.
 	 */
 	public function get_weekday( $weekday_number ) {
-		return $this->weekday[ $weekday_number ];
+		return isset( $this->weekday[ $weekday_number ] ) ? $this->weekday[ $weekday_number ] : '';
 	}
 
 	/**