diff --git a/index.js b/index.js
index 002baf7..fde7e4d 100644
--- a/index.js
+++ b/index.js
@@ -23,6 +23,7 @@ function OptimizeCssAssetsPlugin(options) {
   this.lastCallInstance = new LastCallWebpackPlugin({
     assetProcessors: [
       {
+        phase: LastCallWebpackPlugin.prototype.PHASE.OPTIMIZE_CHUNK_ASSETS,
         regExp: this.options.assetNameRegExp,
         processor: function (assetName, asset, assets) {
           return self.processCss(assetName, asset, assets);