diff --git a/pypaystack/transactions.py b/pypaystack/transactions.py
index 67e4e7f..07f99f7 100644
--- a/pypaystack/transactions.py
+++ b/pypaystack/transactions.py
@@ -69,7 +69,7 @@ def initialize(
         if reference:
             payload.update({"reference": reference})
         if metadata:
-            payload = payload.update({"metadata": {"custom_fields": metadata}})
+            payload.update({"metadata": metadata})
 
         return self._handle_request("POST", url, payload)