diff --git a/src/wp-includes/class-wp-customize-manager.php b/src/wp-includes/class-wp-customize-manager.php
index 55acd10..6507587 100644
--- a/src/wp-includes/class-wp-customize-manager.php
+++ b/src/wp-includes/class-wp-customize-manager.php
@@ -1302,7 +1302,7 @@ final class WP_Customize_Manager {
 	 */
 	protected function _cmp_priority( $a, $b ) {
 		if ( $a->priority === $b->priority ) {
-			return $a->instance_number - $a->instance_number;
+			return $a->instance_number - $b->instance_number;
 		} else {
 			return $a->priority - $b->priority;
 		}