diff --git a/components/_util/props-util.js b/components/_util/props-util.js
index 651109a9a..6211c7bc5 100644
--- a/components/_util/props-util.js
+++ b/components/_util/props-util.js
@@ -217,8 +217,7 @@ export function mergeProps () {
 }
 
 function isValidElement (element) {
-  const name = element.constructor.name
-  return element.tag && (name === 'VNode' || name === 'VueComponent')
+  return element && element.context && element.context._isVue
 }
 
 export {
diff --git a/webpack.site.config.js b/webpack.site.config.js
index 636e7ed6f..59ca57af6 100644
--- a/webpack.site.config.js
+++ b/webpack.site.config.js
@@ -12,7 +12,6 @@ const modulePlugin = new ExtractTextPlugin({
 })
 
 module.exports = merge(baseWebpackConfig, {
-  devtool: '#source-map',
   output: {
     path: path.resolve(__dirname, './dist'),
     publicPath: './',