diff --git a/wp-includes/revision.php b/wp-includes/revision.php
index 9d3ca6f42401..b32163877b6e 100644
--- a/wp-includes/revision.php
+++ b/wp-includes/revision.php
@@ -722,15 +722,23 @@ function _set_preview( $post ) {
  * @access private
  */
 function _show_post_preview() {
+
 	if ( isset( $_GET['preview_id'] ) && isset( $_GET['preview_nonce'] ) ) {
+
+		if ( ! is_user_logged_in() ) {
+			wp_die( __( 'Sorry, you are not allowed to preview drafts. Unauthorized request.' ), 401 );
+		}
+
 		$id = (int) $_GET['preview_id'];
 
 		if ( false === wp_verify_nonce( $_GET['preview_nonce'], 'post_preview_' . $id ) ) {
-			wp_die( __( 'Sorry, you are not allowed to preview drafts.' ), 403 );
+			wp_die( __( 'Sorry, you are not allowed to preview drafts. Nonce is invalid.' ), 403 );
 		}
 
 		add_filter( 'the_preview', '_set_preview' );
+
 	}
+
 }
 
 /**