1 files changed, 1 insertions, 8 deletions
diff --git a/synapse/util/caches/deferred_cache.py b/synapse/util/caches/deferred_cache.py
index 377c9a282a..3c4cc093af 100644
--- a/synapse/util/caches/deferred_cache.py
+++ b/synapse/util/caches/deferred_cache.py
@@ -22,7 +22,6 @@ from typing import (
     Iterable,
     MutableMapping,
     Optional,
-    Sized,
     TypeVar,
     Union,
     cast,
@@ -105,13 +104,7 @@ class DeferredCache(Generic[KT, VT]):
             max_size=max_entries,
             cache_name=name,
             cache_type=cache_type,
-            size_callback=(
-                (lambda d: len(cast(Sized, d)) or 1)
-                # Argument 1 to "len" has incompatible type "VT"; expected "Sized"
-                # We trust that `VT` is `Sized` when `iterable` is `True`
-                if iterable
-                else None
-            ),
+            size_callback=(lambda d: len(d) or 1) if iterable else None,
             metrics_collection_callback=metrics_cb,
             apply_cache_factor_from_config=apply_cache_factor_from_config,
             prune_unread_entries=prune_unread_entries,