diff --git a/torch_dftd/torch_dftd3_calculator.py b/torch_dftd/torch_dftd3_calculator.py
index 5c050ad..a9d5f94 100644
--- a/torch_dftd/torch_dftd3_calculator.py
+++ b/torch_dftd/torch_dftd3_calculator.py
@@ -96,7 +96,7 @@ def _preprocess_atoms(self, atoms: Atoms) -> Dict[str, Optional[Tensor]]:
         Z = torch.tensor(atoms.get_atomic_numbers(), device=self.device)
         if any(atoms.pbc):
             cell: Optional[Tensor] = torch.tensor(
-                atoms.get_cell(), device=self.device, dtype=self.dtype
+                atoms.get_cell().array, device=self.device, dtype=self.dtype
             )
         else:
             cell = None