diff --git a/zarr/_storage/store.py b/zarr/_storage/store.py
index 36a5c0bff5..6faf4a1250 100644
--- a/zarr/_storage/store.py
+++ b/zarr/_storage/store.py
@@ -100,9 +100,7 @@ def _ensure_store(store: Any):
         """
         from zarr.storage import KVStore  # avoid circular import
 
-        if store is None:
-            return None
-        elif isinstance(store, BaseStore):
+        if isinstance(store, BaseStore):
             if not store._store_version == 2:
                 raise ValueError(
                     f"cannot initialize a v2 store with a v{store._store_version} store"
diff --git a/zarr/tests/test_storage.py b/zarr/tests/test_storage.py
index abddb6965c..a3e227ec86 100644
--- a/zarr/tests/test_storage.py
+++ b/zarr/tests/test_storage.py
@@ -73,7 +73,9 @@ class InvalidStore:
     with pytest.raises(ValueError):
         Store._ensure_store(KVStoreV3(dict()))
 
-    assert Store._ensure_store(None) is None
+    # cannot initialize without a store
+    with pytest.raises(ValueError):
+        Store._ensure_store(None)
 
 
 def test_capabilities():