diff --git a/anndata/base.py b/anndata/base.py
index 8b9cd9ca6..fabdb8c2d 100644
--- a/anndata/base.py
+++ b/anndata/base.py
@@ -604,7 +604,7 @@ class AnnData(IndexMixin, metaclass=utils.DeprecationMixinMeta):
 
     def __init__(
         self,
-        X: Optional[Union[np.ndarray, sparse.spmatrix]] = None,
+        X: Optional[Union[np.ndarray, sparse.spmatrix, ArrayView]] = None,
         obs: Optional[Union[pd.DataFrame, Mapping[Any, Iterable[Any]], np.ndarray]] = None,
         var: Optional[Union[pd.DataFrame, Mapping[Any, Iterable[Any]], np.ndarray]] = None,
         uns: Optional[Mapping[Any, Any]] = None,
@@ -868,8 +868,8 @@ def shape(self):
         return self.n_obs, self.n_vars
 
     @property
-    def X(self) -> Union[np.ndarray, sparse.spmatrix, None]:
-        """Data matrix of shape `n_obs` × `n_vars` (`np.ndarray`, `sp.sparse.spmatrix`) or `None`."""
+    def X(self) -> Optional[Union[np.ndarray, sparse.spmatrix, ArrayView]]:
+        """Data matrix of shape `n_obs` × `n_vars`."""
         if self.isbacked:
             if not self.file.isopen: self.file.open()
             X = self.file['X']
diff --git a/anndata/readwrite/write.py b/anndata/readwrite/write.py
index 768b27a2b..2768c0e8b 100644
--- a/anndata/readwrite/write.py
+++ b/anndata/readwrite/write.py
@@ -146,7 +146,7 @@ def preprocess_writing(value):
                 and f[key].shape == value.shape \
                 and f[key].dtype == value.dtype \
                 and not isinstance(f[key], h5py.SparseDataset)
-            if not is_valid_group and not isinstance(value, sparse.spmatrix):
+            if not is_valid_group and not issparse(value):
                 f[key][()] = value
                 return
             else: