diff --git a/src/dom/DefaultDOMPropertyConfig.js b/src/dom/DefaultDOMPropertyConfig.js
index 93af8d1860..d78b46cdc2 100644
--- a/src/dom/DefaultDOMPropertyConfig.js
+++ b/src/dom/DefaultDOMPropertyConfig.js
@@ -41,6 +41,7 @@ var DefaultDOMPropertyConfig = {
     allowFullScreen: MUST_USE_ATTRIBUTE | HAS_BOOLEAN_VALUE,
     allowTransparency: MUST_USE_ATTRIBUTE,
     alt: null,
+    async: HAS_BOOLEAN_VALUE,
     autoComplete: null,
     autoFocus: HAS_BOOLEAN_VALUE,
     autoPlay: HAS_BOOLEAN_VALUE,
@@ -56,6 +57,7 @@ var DefaultDOMPropertyConfig = {
     controls: MUST_USE_PROPERTY | HAS_BOOLEAN_VALUE,
     data: null, // For `<object />` acts as `src`.
     dateTime: MUST_USE_ATTRIBUTE,
+    defer: HAS_BOOLEAN_VALUE,
     dir: null,
     disabled: MUST_USE_ATTRIBUTE | HAS_BOOLEAN_VALUE,
     draggable: null,