diff --git a/lib/worker.js b/lib/worker.js
index 3a7cbc0..db432ba 100644
--- a/lib/worker.js
+++ b/lib/worker.js
@@ -53,8 +53,10 @@ function processMessage(msgLocation, callback) {
     const cacheKey = cache.createCacheKey(source + !!map, message.options);
     // We do not check the cache here because we already determined that this asset yields a cache
     // miss in the parent process.
-    const uglifier = message.options.uglifyES ? require('uglify-es') : require('uglify-js'); // eslint-disable-line global-require, max-len
-    const minifiedContent = minify(source, map, message.options.uglifyJS, uglifier);
+    const uglifyES = message.options.uglifyES;
+    const uglifyJS = message.options.uglifyJS;
+    const uglifier = uglifyES ? require('uglify-es') : require('uglify-js'); // eslint-disable-line global-require, max-len
+    const minifiedContent = minify(source, map, uglifyES || uglifyJS, uglifier);
     cache.saveToCache(cacheKey, JSON.stringify({
       source: minifiedContent.code,
       map: minifiedContent.map,