diff --git a/src/anndata/experimental/backed/_xarray.py b/src/anndata/experimental/backed/_xarray.py
index 48f1dd8e3..59b04b7a0 100644
--- a/src/anndata/experimental/backed/_xarray.py
+++ b/src/anndata/experimental/backed/_xarray.py
@@ -32,7 +32,7 @@ def index(self) -> pd.Index:
     def shape(
         self,
     ):  # aligned mapping classes look for this for DataFrames so this ensures usability with e.g., obsm
-        return [self.dims[get_index_dim(self)], len(self)]
+        return [self.sizes[get_index_dim(self)], len(self)]
 
     @property
     def iloc(self):