diff --git src/wp-includes/class-wp-customize-nav-menus.php src/wp-includes/class-wp-customize-nav-menus.php
index 1a55fa6ce2..d2a346d5b0 100644
--- src/wp-includes/class-wp-customize-nav-menus.php
+++ src/wp-includes/class-wp-customize-nav-menus.php
@@ -324,7 +324,7 @@ final class WP_Customize_Nav_Menus {
 
 		// Prepend list of posts with nav_menus_created_posts search results on first page.
 		$nav_menus_created_posts_setting = $this->manager->get_setting( 'nav_menus_created_posts' );
-		if ( 1 === $args['pagenum'] && $nav_menus_created_posts_setting && count( $nav_menus_created_posts_setting ) > 0 ) {
+		if ( 1 === $args['pagenum'] && $nav_menus_created_posts_setting && count( $nav_menus_created_posts_setting->value() ) > 0 ) {
 			$stub_post_query = new WP_Query(
 				array_merge(
 					$query,
diff --git tests/phpunit/tests/customize/nav-menus.php tests/phpunit/tests/customize/nav-menus.php
index e37b94b09f..a5ebfc92f7 100644
--- tests/phpunit/tests/customize/nav-menus.php
+++ tests/phpunit/tests/customize/nav-menus.php
@@ -297,6 +297,7 @@ class Test_WP_Customize_Nav_Menus extends WP_UnitTestCase {
 	 */
 	function test_search_available_items_query() {
 		$menus = new WP_Customize_Nav_Menus( $this->wp_customize );
+		do_action( 'customize_register', $this->wp_customize );
 
 		// Create posts.
 		$post_ids   = array();