Ticket #20496: 20496.2.diff

src/wp-includes/canonical.php

@@ -78 +78 @@
         if ( !isset($redirect['query']) )
                 $redirect['query'] = '';
 
-        // If its not a preview then remove it from URL
-        if ( ! is_preview() ) {
+        // It's not a preview, so remove it from URL
+        if ( get_query_var( 'preview' ) ) {
                 $redirect['query'] = remove_query_arg( 'preview', $redirect['query'] );
         }