diff --git a/pineappl_py/src/import_subgrid.rs b/pineappl_py/src/import_subgrid.rs
index 6cef84e3..d3721a81 100644
--- a/pineappl_py/src/import_subgrid.rs
+++ b/pineappl_py/src/import_subgrid.rs
@@ -1,7 +1,7 @@
 //! PyPackedSubgrid* interface.
 
 use super::subgrid::PySubgridEnum;
-use numpy::PyReadonlyArray3;
+use numpy::{PyReadonlyArray2, PyReadonlyArray3};
 use pineappl::import_subgrid::ImportSubgridV1;
 use pineappl::packed_array::PackedArray;
 use pyo3::prelude::*;
@@ -18,6 +18,8 @@ pub struct PyImportSubgridV1 {
 impl PyImportSubgridV1 {
     /// Constructor.
     ///
+    /// # Panics
+    ///
     /// Parameters
     /// ----------
     /// array : numpy.ndarray(float)
@@ -26,25 +28,58 @@ impl PyImportSubgridV1 {
     ///     scales grid
     /// x1_grid : list(float)
     ///     first momentum fraction grid
-    /// x2_grid : list(float)
+    /// x2_grid : Optional(list(float))
     ///     second momentum fraction grid
     #[new]
-    pub fn new(
-        array: PyReadonlyArray3<f64>,
+    #[must_use]
+    pub fn new<'py>(
+        array: PyObject,
         scales: Vec<f64>,
         x1_grid: Vec<f64>,
-        x2_grid: Vec<f64>,
+        x2_grid: Option<Vec<f64>>,
+        py: Python<'py>,
     ) -> Self {
-        let node_values: Vec<Vec<f64>> = vec![scales, x1_grid, x2_grid];
+        // let node_values: Vec<Vec<f64>> = vec![scales, x1_grid, x2_grid];
+        // let mut sparse_array: PackedArray<f64> =
+        //     PackedArray::new(node_values.iter().map(Vec::len).collect());
+
+        // for ((iscale, ix1, ix2), value) in array
+        //     .as_array()
+        //     .indexed_iter()
+        //     .filter(|((_, _, _), value)| **value != 0.0)
+        // {
+        //     sparse_array[[iscale, ix1, ix2]] = *value;
+        // }
+
+        // Self {
+        //     import_subgrid: ImportSubgridV1::new(sparse_array, node_values),
+        // }
+        let mut node_values: Vec<Vec<f64>> = vec![scales, x1_grid];
+
+        if let Some(x2) = x2_grid {
+            node_values.push(x2);
+        }
         let mut sparse_array: PackedArray<f64> =
             PackedArray::new(node_values.iter().map(Vec::len).collect());
 
-        for ((iscale, ix1, ix2), value) in array
-            .as_array()
-            .indexed_iter()
-            .filter(|((_, _, _), value)| **value != 0.0)
-        {
-            sparse_array[[iscale, ix1, ix2]] = *value;
+        if sparse_array.shape().to_vec().len() == 3 {
+            let array_3d: PyReadonlyArray3<f64> = array.extract(py).unwrap();
+            for ((iscale, ix1, ix2), value) in array_3d
+                .as_array()
+                .indexed_iter()
+                .filter(|((_, _, _), value)| **value != 0.0)
+            {
+                sparse_array[[iscale, ix1, ix2]] = *value;
+            }
+        } else {
+            let array_2d: PyReadonlyArray2<f64> = array.extract(py).unwrap();
+            for ((iscale, ix1), value) in array_2d
+                .as_array()
+                .indexed_iter()
+                .filter(|((_, _), value)| **value != 0.0)
+            {
+                sparse_array[[iscale, ix1]] = *value;
+            }
         }
 
         Self {
diff --git a/pineappl_py/tests/test_fk_table.py b/pineappl_py/tests/test_fk_table.py
index fdde8d4f..ac61e166 100644
--- a/pineappl_py/tests/test_fk_table.py
+++ b/pineappl_py/tests/test_fk_table.py
@@ -86,10 +86,9 @@ def test_convolve(self):
         xs = np.linspace(0.5, 1.0, 5)
         vs = xs.copy()
         subgrid = ImportSubgridV1(
-            vs[np.newaxis, :, np.newaxis],
+            vs[np.newaxis, :],  # DIS shape: (len(q2), len(x_grid))
             np.array([90.0]),
             xs,
-            np.array([1.0]),
         )
         g.set_subgrid(0, 0, 0, subgrid.into())