diff --git a/docs/layout/tools/template-converter.js b/docs/layout/tools/template-converter.js
index 55217ba3..b1739462 100644
--- a/docs/layout/tools/template-converter.js
+++ b/docs/layout/tools/template-converter.js
@@ -68,7 +68,7 @@ window.templateConverter = (function () {
 
 			if (el.attrs.class) {
 				virtual += "." + el.attrs.class.replace(/\s+/g, ".")
-				el.attrs.class = undefined
+				delete el.attrs.class
 			}
 
 			each(Object.keys(el.attrs).sort(), function (attrName) {