diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-widgets-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-widgets-controller.php
index b3bd5ae5ac..5fb9b8f6e1 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-widgets-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-widgets-controller.php
@@ -109,6 +109,8 @@ class WP_REST_Widgets_Controller extends WP_REST_Controller {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function get_items( $request ) {
+		retrieve_widgets();
+
 		$prepared = array();
 
 		foreach ( wp_get_sidebars_widgets() as $sidebar_id => $widget_ids ) {
@@ -149,6 +151,8 @@ class WP_REST_Widgets_Controller extends WP_REST_Controller {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function get_item( $request ) {
+		retrieve_widgets();
+
 		$widget_id  = $request['id'];
 		$sidebar_id = wp_find_widgets_sidebar( $widget_id );
 
@@ -230,6 +234,8 @@ class WP_REST_Widgets_Controller extends WP_REST_Controller {
 	public function update_item( $request ) {
 		global $wp_widget_factory;
 
+		retrieve_widgets();
+
 		$widget_id  = $request['id'];
 		$sidebar_id = wp_find_widgets_sidebar( $widget_id );
 
@@ -291,6 +297,8 @@ class WP_REST_Widgets_Controller extends WP_REST_Controller {
 	public function delete_item( $request ) {
 		global $wp_registered_widget_updates;
 
+		retrieve_widgets();
+
 		$widget_id  = $request['id'];
 		$sidebar_id = wp_find_widgets_sidebar( $widget_id );
 
diff --git a/tests/phpunit/tests/rest-api/rest-widgets-controller.php b/tests/phpunit/tests/rest-api/rest-widgets-controller.php
index fc815e7aa2..594458598b 100644
--- a/tests/phpunit/tests/rest-api/rest-widgets-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-widgets-controller.php
@@ -95,20 +95,14 @@ class WP_Test_REST_Widgets_Controller extends WP_Test_REST_Controller_Testcase {
 	}
 
 	public function setUp() {
-		global $wp_registered_widgets, $wp_registered_sidebars, $_wp_sidebars_widgets, $wp_widget_factory;
+		global $wp_widget_factory;
 
 		parent::setUp();
 
 		wp_set_current_user( self::$admin_id );
 
-		// Unregister all widgets and sidebars.
-		$wp_registered_widgets  = array();
-		$wp_registered_sidebars = array();
-		$_wp_sidebars_widgets   = array();
-		update_option( 'sidebars_widgets', array() );
-
 		// Re-register core widgets.
-		$wp_widget_factory->_register_widgets();
+		wp_widgets_init();
 
 		// Register a non-multi widget for testing.
 		wp_register_widget_control(
@@ -149,6 +143,27 @@ class WP_Test_REST_Widgets_Controller extends WP_Test_REST_Controller_Testcase {
 		);
 	}
 
+	public function clean_up_global_scope() {
+		global
+			$wp_widget_factory,
+			$wp_registered_sidebars,
+			$wp_registered_widgets,
+			$wp_registered_widget_controls,
+			$wp_registered_widget_updates,
+			$_wp_sidebars_widgets;
+
+		$wp_registered_sidebars        = array();
+		$wp_registered_widgets         = array();
+		$wp_registered_widget_controls = array();
+		$wp_registered_widget_updates  = array();
+		$wp_widget_factory->widgets    = array();
+		$_wp_sidebars_widgets          = array();
+
+		update_option( 'sidebars_widgets', array() );
+
+		parent::clean_up_global_scope();
+	}
+
 	private function setup_widget( $id_base, $number, $settings ) {
 		global $wp_widget_factory;