diff --git a/xarray/backends/zarr.py b/xarray/backends/zarr.py
index 8b83f2b755d..b3d2d3af413 100644
--- a/xarray/backends/zarr.py
+++ b/xarray/backends/zarr.py
@@ -750,7 +750,7 @@ def __init__(
         self._close_store_on_close = close_store_on_close
         self._use_zarr_fill_value_as_mask = use_zarr_fill_value_as_mask
 
-        self._cache: dict[str, tuple[str, ...]] = {}
+        self._cache: dict[str, None | tuple[str, ...]] = {}
         if cache_array_keys:
             self._cache["array_keys"] = None