diff --git a/src/azul/service/avro_pfb.py b/src/azul/service/avro_pfb.py
index 5d21ee973..1e64ef8c8 100644
--- a/src/azul/service/avro_pfb.py
+++ b/src/azul/service/avro_pfb.py
@@ -644,7 +644,7 @@ def _entity_schema_recursive(field_types: FieldTypes,
 
 def _update_replica_schema(*,
                            schema: MutableJSON,
-                           path: Sequence[str],
+                           path: tuple[str, ...],
                            key: str,
                            value: AnyMutableJSON):
     """
@@ -652,7 +652,7 @@ def _update_replica_schema(*,
     accommodates a given (part of a) JSON document. The schema will only ever
     expand, so after updating it will describe a superset of the documents that
     it described pre-update. Starting from an empty schema, repeatedly calling
-    this function this allows us to discover a general schema for a series of
+    this function allows us to discover a general schema for a series of
     documents of unknown shape.
 
     :param schema: a part of a PFB schema. It may be empty.
@@ -723,7 +723,7 @@ def _update_replica_schema(*,
 
 
 def _new_replica_schema(*,
-                        path: Sequence[str],
+                        path: tuple[str, ...],
                         value: AnyJSON,
                         ) -> AnyMutableJSON:
     """