diff --git a/zarr/_storage/store.py b/zarr/_storage/store.py
index 6f5bf78e28..a473424772 100644
--- a/zarr/_storage/store.py
+++ b/zarr/_storage/store.py
@@ -118,11 +118,11 @@ class Store(BaseStore):
 
     """
 
-    def listdir(self, path: str = "") -> List[str]:
+    def listdir(self, path: str = None) -> List[str]:
         path = normalize_storage_path(path)
         return _listdir_from_keys(self, path)
 
-    def rmdir(self, path: str = "") -> None:
+    def rmdir(self, path: str = None) -> None:
         if not self.is_erasable():
             raise NotImplementedError(
                 f'{type(self)} is not erasable, cannot call "rmdir"'
@@ -150,14 +150,6 @@ def _rename_from_keys(store: BaseStore, src_path: str, dst_path: str) -> None:
             store[new_key] = store.pop(key)
 
 
-def _rmdir_from_keys(store: Union[BaseStore, MutableMapping], path: Optional[str] = None) -> None:
-    # assume path already normalized
-    prefix = _path_to_prefix(path)
-    for key in list(store.keys()):
-        if key.startswith(prefix):
-            del store[key]
-
-
 def _listdir_from_keys(store: BaseStore, path: Optional[str] = None) -> List[str]:
     # assume path already normalized
     prefix = _path_to_prefix(path)
@@ -168,3 +160,11 @@ def _listdir_from_keys(store: BaseStore, path: Optional[str] = None) -> List[str
             child = suffix.split('/')[0]
             children.add(child)
     return sorted(children)
+
+
+def _rmdir_from_keys(store: Union[BaseStore, MutableMapping], path: Optional[str] = None) -> None:
+    # assume path already normalized
+    prefix = _path_to_prefix(path)
+    for key in list(store.keys()):
+        if key.startswith(prefix):
+            del store[key]
diff --git a/zarr/storage.py b/zarr/storage.py
index b5da03701c..951bb1ffc3 100644
--- a/zarr/storage.py
+++ b/zarr/storage.py
@@ -128,7 +128,7 @@ def normalize_store_arg(store: Any, clobber=False, storage_options=None, mode="w
         return store
 
 
-def rmdir(store: StoreLike, path: Path = None):
+def rmdir(store: StoreLike, path: str = None):
     """Remove all items under the given path. If `store` provides a `rmdir` method,
     this will be called, otherwise will fall back to implementation via the
     `Store` interface."""
@@ -155,7 +155,7 @@ def rename(store: BaseStore, src_path: Path, dst_path: Path):
         _rename_from_keys(store, src_path, dst_path)
 
 
-def listdir(store: BaseStore, path: Path = None):
+def listdir(store: BaseStore, path: str = None):
     """Obtain a directory listing for the given path. If `store` provides a `listdir`
     method, this will be called, otherwise will fall back to implementation via the
     `MutableMapping` interface."""
@@ -694,7 +694,7 @@ def __iter__(self):
     def __len__(self) -> int:
         return sum(1 for _ in self.keys())
 
-    def listdir(self, path: Path = None) -> List[str]:
+    def listdir(self, path: str = None) -> List[str]:
         path = normalize_storage_path(path)
         if path:
             try:
@@ -718,7 +718,7 @@ def rename(self, src_path: Path, dst_path: Path):
 
         dst_parent[dst_key] = src_parent.pop(src_key)
 
-    def rmdir(self, path: Path = None):
+    def rmdir(self, path: str = None):
         path = normalize_storage_path(path)
         if path:
             try:
@@ -2157,7 +2157,7 @@ def _keys(self):
             self._keys_cache = list(self._store.keys())
         return self._keys_cache
 
-    def listdir(self, path: Path = None):
+    def listdir(self, path: str = None) -> List[str]:
         with self._mutex:
             try:
                 return self._listdir_cache[path]
@@ -2682,5 +2682,5 @@ def __setitem__(self, key, value):
     def getsize(self, path):
         return getsize(self.meta_store, path)
 
-    def listdir(self, path):
+    def listdir(self, path=None):
         return listdir(self.meta_store, path)