diff --git a/karton/core/backend.py b/karton/core/backend.py
index 2c1b33f..d678898 100644
--- a/karton/core/backend.py
+++ b/karton/core/backend.py
@@ -532,21 +532,15 @@ def get_all_tasks(
             self.iter_all_tasks(chunk_size=chunk_size, parse_resources=parse_resources)
         )
 
-    def iter_task_tree(
+    def _iter_legacy_task_tree(
         self, root_uid: str, chunk_size: int = 1000, parse_resources: bool = True
     ) -> Iterator[Task]:
         """
-        Iterates all tasks that belong to the same analysis task tree
-        and have the same root_uid
+        Processes tasks made by <5.4.0 (unrouted from <5.4.0 producers or existing
+        before upgrade)
 
-        :param root_uid: Root identifier of task tree
-        :param chunk_size: Size of chunks passed to the Redis SCAN and MGET command
-        :param parse_resources: If set to False, resources are not parsed.
-            It speeds up deserialization. Read :py:meth:`Task.unserialize` documentation
-            to learn more.
-        :return: Iterator with task objects
+        Used internally by iter_task_tree.
         """
-        # Process unrouted tasks produced by Karton <5.4.0
         legacy_task_keys = self.redis.scan_iter(
             match=f"{KARTON_TASK_NAMESPACE}:*[^:]*", count=chunk_size
         )
@@ -554,13 +548,31 @@ def iter_task_tree(
             yield from filter(
                 lambda task: task.root_uid == root_uid,
                 (
-                    Task.unserialize(task_data, backend=self)
-                    if parse_resources
-                    else Task.unserialize(task_data, parse_resources=False)
+                    Task.unserialize(task_data, parse_resources=parse_resources)
                     for task_data in self.redis.mget(chunk)
                     if task_data is not None
                 ),
             )
+
+    def iter_task_tree(
+        self, root_uid: str, chunk_size: int = 1000, parse_resources: bool = True
+    ) -> Iterator[Task]:
+        """
+        Iterates all tasks that belong to the same analysis task tree
+        and have the same root_uid
+
+        :param root_uid: Root identifier of task tree
+        :param chunk_size: Size of chunks passed to the Redis SCAN and MGET command
+        :param parse_resources: If set to False, resources are not parsed.
+            It speeds up deserialization. Read :py:meth:`Task.unserialize` documentation
+            to learn more.
+        :return: Iterator with task objects
+        """
+        # Process <5.4.0 tasks (unrouted from <5.4.0 producers
+        # or existing before upgrade)
+        yield from self._iter_legacy_task_tree(
+            root_uid, chunk_size=chunk_size, parse_resources=parse_resources
+        )
         # Process >=5.4.0 tasks
         task_keys = self.redis.scan_iter(
             match=f"{KARTON_TASK_NAMESPACE}:{{{root_uid}}}:*", count=chunk_size