diff --git a/packages/bundler-mako/index.js b/packages/bundler-mako/index.js
index 0f95636e4..7c83502bb 100644
--- a/packages/bundler-mako/index.js
+++ b/packages/bundler-mako/index.js
@@ -680,7 +680,7 @@ async function getMakoConfig(opts) {
     ...mako,
   };
 
-  return makoConfig;
+  return lodash.merge(makoConfig, mako);
 }
 
 function getLessSourceMapConfig(devtool) {