diff --git a/CHANGELOG.asciidoc b/CHANGELOG.asciidoc
index 0355fb0a3..9d84ad835 100644
--- a/CHANGELOG.asciidoc
+++ b/CHANGELOG.asciidoc
@@ -33,8 +33,10 @@ endif::[]
 
 // Unreleased changes go here
 // When the next release happens, nest these changes under the "Python Agent version 6.x" heading
-//[float]
-//===== Features
+[float]
+===== Features
+
+* Add `transport_json_serializer` configuration option {pull}1777[#1777]
 
 [float]
 ===== Bug fixes
diff --git a/elasticapm/base.py b/elasticapm/base.py
index 0ca00e5f5..355e2016e 100644
--- a/elasticapm/base.py
+++ b/elasticapm/base.py
@@ -152,7 +152,7 @@ def __init__(self, config=None, **inline):
             "processors": self.load_processors(),
         }
         if config.transport_json_serializer:
-            transport_kwargs['json_serializer'] = config.transport_json_serializer
+            transport_kwargs["json_serializer"] = config.transport_json_serializer
 
         self._api_endpoint_url = urllib.parse.urljoin(
             self.config.server_url if self.config.server_url.endswith("/") else self.config.server_url + "/",