diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
index e63b6c9975f..3becce7e432 100644
--- a/xarray/core/dataarray.py
+++ b/xarray/core/dataarray.py
@@ -2244,7 +2244,7 @@ def to_masked_array(self, copy: bool = True) -> np.ma.MaskedArray:
         isnull = pd.isnull(values)
         return np.ma.MaskedArray(data=values, mask=isnull, copy=copy)
 
-    def to_netcdf(self, *args, **kwargs) -> Optional["Delayed"]:
+    def to_netcdf(self, *args, **kwargs) -> Union[bytes, "Delayed", None]:
         """Write DataArray contents to a netCDF file.
 
         All parameters are passed directly to `xarray.Dataset.to_netcdf`.