diff --git a/dask_kubernetes/operator/controller/controller.py b/dask_kubernetes/operator/controller/controller.py
index 00968d36..0dc01fd9 100644
--- a/dask_kubernetes/operator/controller/controller.py
+++ b/dask_kubernetes/operator/controller/controller.py
@@ -489,6 +489,8 @@ async def retire_workers(
                 attribute="name",
             )
             await scheduler_comm.retire_workers(names=workers_to_close)
+            if isinstance(workers_to_close, tuple):
+                workers_to_close = list(workers_to_close)
             assert isinstance(workers_to_close, list)
             return workers_to_close