diff --git a/README.md b/README.md
index 6da2a41..e1661f5 100644
--- a/README.md
+++ b/README.md
@@ -77,6 +77,8 @@ module.exports = {
 };
 ```
 
+The `transformer` field accepts a function and optionally you may provide an `async` function.
+
 # Feedback
 
 This is the very first version of our plugin and isn't yet officially supported. Please leave all your feedback in GitHub issues 😊
diff --git a/gatsby-node.js b/gatsby-node.js
index 1941cc2..9b29589 100644
--- a/gatsby-node.js
+++ b/gatsby-node.js
@@ -43,7 +43,7 @@ exports.onPostBuild = async function(
     if (result.errors) {
       report.panic(`failed to index to Algolia`, result.errors);
     }
-    const objects = transformer(result);
+    const objects = await transformer(result);
     const chunks = chunk(objects, chunkSize);
 
     setStatus(activity, `query ${i}: splitting in ${chunks.length} jobs`);