diff --git a/smmregrid/gridtype.py b/smmregrid/gridtype.py
index a0f7300..2a18744 100644
--- a/smmregrid/gridtype.py
+++ b/smmregrid/gridtype.py
@@ -45,7 +45,8 @@ def _handle_default_dimensions(self, extra_dims):
 
         update_dims = DEFAULT_DIMS
         for dim in extra_dims.keys():
-            update_dims[dim] = update_dims[dim] + extra_dims[dim]
+            if  extra_dims[dim]:
+                update_dims[dim] = update_dims[dim] + extra_dims[dim]
         return update_dims
                      
     def __eq__(self, other):
diff --git a/smmregrid/regrid.py b/smmregrid/regrid.py
index f2f37c7..3483f13 100644
--- a/smmregrid/regrid.py
+++ b/smmregrid/regrid.py
@@ -143,7 +143,12 @@ def __init__(self, source_grid=None, target_grid=None, weights=None,
                     source_grid_array_to_cdo = source_grid
                 else:
                     # when feeding from xarray, select the variable and its bounds
-                    source_grid_array_to_cdo = source_grid_array[[list(gridtype.variables.keys())[0]] + gridtype.bounds]
+                    if isinstance(source_grid_array, xarray.Dataset):
+                        stored_vars = [list(gridtype.variables.keys())[0]] + gridtype.bounds
+                        self.loggy.debug('Storing variables %s', stored_vars)
+                        source_grid_array_to_cdo = source_grid_array[stored_vars]
+                    else:
+                        source_grid_array_to_cdo = source_grid_array
 
                 gridtype.weights = cdo_generate_weights(source_grid_array_to_cdo, target_grid, method=method,
                                                         vertical_dim=gridtype.vertical_dim,
diff --git a/tests/basic_test.py b/tests/basic_test.py
index 142c8c0..e9f429c 100644
--- a/tests/basic_test.py
+++ b/tests/basic_test.py
@@ -25,7 +25,7 @@ def test_healpix_extra(method):
     rfield = interpolator.regrid(xfield)
     assert rfield['tas'].shape == (2, 180, 360)
 
-@pytest.mark.parametrize("method", ['con', 'nn', 'bil'])
+@pytest.mark.parametrize("method", ['con', 'nn', 'bic'])
 def test_nan_preserve(method):
     """Test to verify that NaN are preserved"""
     xfield = xarray.open_mfdataset(os.path.join(INDIR, 'tas-ecearth.nc'))
@@ -34,3 +34,10 @@ def test_nan_preserve(method):
     interpolator = Regridder(weights=wfield, space_dims='pippo', loglevel='debug')
     rfield = interpolator.regrid(xfield)
     assert numpy.isnan(rfield['tas'][1,:,:]).all().compute()
+
+@pytest.mark.parametrize("method", ['nn'])
+def test_datarray(method):
+    xfield = xarray.open_mfdataset(os.path.join(INDIR, 'tas-ecearth.nc'))
+    interpolator = Regridder(source_grid=xfield['tas'], target_grid=tfile, loglevel='debug', method = method)
+    interp = interpolator.regrid(source_data=xfield)
+    assert interp['tas'].shape == (12, 180, 360)