diff --git a/lib/makeWebpackConfig.js b/lib/makeWebpackConfig.js
index cf12ca6d..282f7c92 100644
--- a/lib/makeWebpackConfig.js
+++ b/lib/makeWebpackConfig.js
@@ -171,7 +171,7 @@ module.exports = async (playroomConfig, options) => {
   };
 
   const theirConfig = playroomConfig.webpackConfig
-    ? playroomConfig.webpackConfig()
+    ? await playroomConfig.webpackConfig()
     : makeDefaultWebpackConfig(playroomConfig);
 
   return merge(ourConfig, theirConfig);