diff --git a/lib/Element/prototype/extend.js b/lib/Element/prototype/extend.js
index <HASH>..<HASH> 100644
--- a/lib/Element/prototype/extend.js
+++ b/lib/Element/prototype/extend.js
@@ -24,9 +24,10 @@ module.exports = function (attrs/*, …children*/) {
 			} else if (typeof value === 'boolean') {
 				if (value) {
 					this.setAttribute(name, name);
+					this[name] = true;
 				} else {
 					this.removeAttribute(name);
-					delete this[name];
+					this[name] = false;
 				}
 			} else {
 				this.setAttribute(name, value);
Boolean properties must not be deleted but set

Deletion introduced bugs in some engines (no suprise)