diff --git a/changelog.d/15275.misc b/changelog.d/15275.misc
new file mode 100644
index 000000000..b222acd72
--- /dev/null
+++ b/changelog.d/15275.misc
@@ -0,0 +1 @@
+Make `configure_workers_and_start` script used in Complement tests compatible with older versions of Python.
\ No newline at end of file
diff --git a/docker/configure_workers_and_start.py b/docker/configure_workers_and_start.py
index cfb16c2e2..376f9ed63 100755
--- a/docker/configure_workers_and_start.py
+++ b/docker/configure_workers_and_start.py
@@ -422,7 +422,7 @@ def add_worker_roles_to_shared_config(
 
 
 def merge_worker_template_configs(
-    existing_dict: Dict[str, Any] | None,
+    existing_dict: Optional[Dict[str, Any]],
     to_be_merged_dict: Dict[str, Any],
 ) -> Dict[str, Any]:
     """When given an existing dict of worker template configuration consisting with both