diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
index 4eca50b549..c4155ad63d 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-plugins-controller.php
@@ -209,6 +209,8 @@ class WP_REST_Plugins_Controller extends WP_REST_Controller {
 	 * @return true|WP_Error True if can read, a WP_Error instance otherwise.
 	 */
 	protected function check_read_permission( $plugin ) {
+		require_once ABSPATH . 'wp-admin/includes/plugin.php';
+
 		if ( ! $this->is_plugin_installed( $plugin ) ) {
 			return new WP_Error( 'rest_plugin_not_found', __( 'Plugin not found.' ), array( 'status' => 404 ) );
 		}