Index: branches/5.2.x/core/admin_templates/languages/email_template_settings.tpl
===================================================================
diff -u -N -r15608 -r15858
--- branches/5.2.x/core/admin_templates/languages/email_template_settings.tpl	(.../email_template_settings.tpl)	(revision 15608)
+++ branches/5.2.x/core/admin_templates/languages/email_template_settings.tpl	(.../email_template_settings.tpl)	(revision 15858)
@@ -186,7 +186,7 @@
 	// enable all disabled controls before submit
 	Application.setHook('email-template:*',
 		function () {
-			$(':input:disabled').attr('disabled', '');
+			$(':input:disabled').prop('disabled', false);
 		}
 	)
 </script>