diff --git a/eryx/pdb.py b/eryx/pdb.py
index 73de8be..a630cb8 100644
--- a/eryx/pdb.py
+++ b/eryx/pdb.py
@@ -147,7 +147,7 @@ def _extract_cell(self):
         Extract unit cell information.
         """
         self.cell = np.array(self.structure.cell.parameters)
-        self.A_inv = np.array(self.structure.cell.fractionalization_matrix)
+        self.A_inv = np.array(self.structure.cell.frac.mat)
         self.space_group = self.structure.spacegroup_hm
         self.unit_cell_axes = get_unit_cell_axes(self.cell)