diff --git a/wagtail/wagtailadmin/static_src/wagtailadmin/js/page-editor.js b/wagtail/wagtailadmin/static_src/wagtailadmin/js/page-editor.js
index 20c495bd2..7bf427b5e 100644
--- a/wagtail/wagtailadmin/static_src/wagtailadmin/js/page-editor.js
+++ b/wagtail/wagtailadmin/static_src/wagtailadmin/js/page-editor.js
@@ -461,6 +461,7 @@ $(function() {
 
                     } else {
                         previewWindow.close();
+                        disableDirtyFormCheck();
                         document.open();
                         document.write(data);
                         document.close();