diff --git a/src/nomad_simulations/schema_packages/basis_set.py b/src/nomad_simulations/schema_packages/basis_set.py
index c66df084..54b19cc6 100644
--- a/src/nomad_simulations/schema_packages/basis_set.py
+++ b/src/nomad_simulations/schema_packages/basis_set.py
@@ -225,9 +225,15 @@ class APWBaseOrbital(ArchiveSection):
         """,
     )  # TODO: add check non-negative # ? to remove
 
+    def _get_open_quantities(self) -> set[str]:
+        """Extract the open quantities of the `APWBaseOrbital`."""
+        return {
+            k for k, v in self.m_def.all_quantities.items() if self.m_get(v) is not None
+        }
+
     def _get_lengths(self, quantities: set[str]) -> list[int]:
         """Extract the lengths of the `quantities` contained in the set."""
-        present_quantities = set(quantities) & self.m_quantities
+        present_quantities = set(quantities) & self._get_open_quantities()
         lengths: list[int] = []
         for quant in present_quantities:
             length = len(getattr(self, quant))
@@ -235,7 +241,7 @@ def _get_lengths(self, quantities: set[str]) -> list[int]:
                 lengths.append(length)
         return lengths
 
-    def _of_equal_length(lengths: list[int]) -> bool:
+    def _of_equal_length(self, lengths: list[int]) -> bool:
         """Check if all elements in the list are of equal length."""
         if len(lengths) == 0:
             return True
@@ -266,9 +272,10 @@ def normalize(self, archive: EntryArchive, logger: BoundLogger) -> None:
         if self.n_terms is None:
             self.n_terms = new_n_terms
         elif self.n_terms != new_n_terms:
-            logger.error(
-                f'Inconsistent lengths of `APWBaseOrbital` quantities: {self.m_quantities}. Setting back to `None`.'
-            )
+            if logger is not None:
+                logger.error(
+                    f'Inconsistent lengths of `APWBaseOrbital` quantities: {self.m_def.quantities}. Setting back to `None`.'
+                )
             self.n_terms = None
 
         # enforce differential order constraints
diff --git a/tests/test_basis_set.py b/tests/test_basis_set.py
index 51f02302..dc7ee6ec 100644
--- a/tests/test_basis_set.py
+++ b/tests/test_basis_set.py
@@ -93,6 +93,39 @@ def test_full_apw(
     numerical_settings = entry.data.model_method[0].numerical_settings
     numerical_settings.append(generate_apw(species_def, cutoff=cutoff))
 
+    # test structure
     assert (
         numerical_settings[0].m_to_dict() == refs_apw[ref_index]
     )  # TODO: add normalization?
+
+
+@pytest.mark.parametrize(
+    'ref_n_terms, e, e_n, d_o',
+    [
+        (None, [0.0], [0, 0], []),  # logically inconsistent
+        (1, [0.0], [0], [0]),  # apw
+        (2, [0.0, 0.0], [0, 0], [0, 1]),  # lapw
+    ],
+)
+def test_apw_base_orbital(
+    ref_n_terms: Optional[int], e: list[float], e_n: list[int], d_o: list[int]
+):
+    orb = APWBaseOrbital(
+        energy_parameter=e,
+        energy_parameter_n=e_n,
+        differential_order=d_o,
+    )
+
+    assert orb.get_n_terms() == ref_n_terms
+
+
+@pytest.mark.parametrize('n_terms, ref_n_terms', [(None, 1), (1, 1), (2, None)])
+def test_apw_base_orbital_normalize(n_terms: Optional[int], ref_n_terms: Optional[int]):
+    orb = APWBaseOrbital(
+        n_terms=n_terms,
+        energy_parameter=[0],
+        energy_parameter_n=[0],
+        differential_order=[1],
+    )
+    orb.normalize(None, logger)
+    assert orb.n_terms == ref_n_terms