diff --git a/lib/style-rewriter.js b/lib/style-rewriter.js
index c631857..1195799 100644
--- a/lib/style-rewriter.js
+++ b/lib/style-rewriter.js
@@ -40,7 +40,7 @@ var addId = postcss.plugin('add-id', function () {
  */
 
 module.exports = function (id, css, scoped, options) {
-  var key = id + '!!' + css
+  var key = id + '!!' + scoped + '!!' + css
   var val = cache.get(key)
   if (val) {
     return Promise.resolve(val)
@@ -56,9 +56,16 @@ module.exports = function (id, css, scoped, options) {
     }
 
     // scoped css rewrite
-    if (scoped) {
+    // make sure the addId plugin is only pushed once
+    if (scoped && plugins.indexOf(addId) === -1) {
       plugins.push(addId)
     }
+
+    // remove the addId plugin if the style block is not scoped
+    if (!scoped && plugins.indexOf(addId) !== -1) {
+      plugins.splice(plugins.indexOf(addId), 1)
+    }
+
     // minification
     if (process.env.NODE_ENV === 'production') {
       plugins.push(require('cssnano')(assign({