diff --git a/lib/clean.js b/lib/clean.js
index 7f2d5440b..8cdb4b793 100644
--- a/lib/clean.js
+++ b/lib/clean.js
@@ -49,14 +49,16 @@ var CleanCSS = module.exports = function CleanCSS(options) {
 
 // for compatibility with optimize-css-assets-webpack-plugin
 CleanCSS.process = function (input, opts) {
+  var cleanCss;
   var optsTo = opts.to;
+
   delete opts.to;
+  cleanCss = new CleanCSS(Object.assign({ returnPromise: true, rebaseTo: optsTo }, opts));
 
-  var cleanCss = new CleanCSS(Object.assign({ returnPromise: true, rebaseTo: optsTo }, opts));
   return cleanCss.minify(input)
-  .then(function(output) {
-    return { css: output.styles };
-  });
+    .then(function(output) {
+      return { css: output.styles };
+    });
 };