diff --git a/espei/error_functions/non_equilibrium_thermochemical_error.py b/espei/error_functions/non_equilibrium_thermochemical_error.py
index 0de62e7b..2df0e871 100644
--- a/espei/error_functions/non_equilibrium_thermochemical_error.py
+++ b/espei/error_functions/non_equilibrium_thermochemical_error.py
@@ -475,7 +475,7 @@ def __init__(
             comps = sorted(phase_models.components)
             model_dict = phase_models.get_model_dict()
         else:
-            comps = sorted(database.elements)
+            comps = sorted(set(database.elements) - {'/-'})
             model_dict = dict()
         phases = sorted(filter_phases(database, unpack_species(database, comps), database.phases.keys()))
         if symbols_to_fit is None:
@@ -504,4 +504,4 @@ def get_likelihood(self, parameters) -> float:
         return likelihood
 
 
-residual_function_registry.register(FixedConfigurationPropertyResidual)
\ No newline at end of file
+residual_function_registry.register(FixedConfigurationPropertyResidual)
diff --git a/espei/error_functions/zpf_error.py b/espei/error_functions/zpf_error.py
index 12e915eb..7820e48b 100644
--- a/espei/error_functions/zpf_error.py
+++ b/espei/error_functions/zpf_error.py
@@ -436,6 +436,8 @@ def __init__(
         self.zpf_data = get_zpf_data(database, comps, phases, datasets, parameters, model_dict)
 
     def get_residuals(self, parameters: ArrayLike) -> Tuple[List[float], List[float]]:
+        if len(self.zpf_data) == 0:
+            return [], []
         driving_forces, weights = calculate_zpf_driving_forces(self.zpf_data, parameters, short_circuit=True)
         # Driving forces and weights are 2D ragged arrays with the shape (len(zpf_data), len(zpf_data['values']))
         residuals = np.concatenate(driving_forces).tolist()
diff --git a/tests/test_error_functions.py b/tests/test_error_functions.py
index 289bd5d3..385f2d39 100644
--- a/tests/test_error_functions.py
+++ b/tests/test_error_functions.py
@@ -128,6 +128,25 @@ def test_fixed_configuration_residual_with_internal_degrees_of_freedom(datasets_
     assert np.allclose(residuals, [0.0])
 
 
+def test_fixed_configuration_residual_with_electron_element(datasets_db):
+    """Fixed configuration residuals work for databases that declare the electron (/-)"""
+    dbf = Database("ELEMENT /- ELECTRON_GAS 0.0 0.0 0.0 !\n" + A_B_REGULAR_SOLUTION_TDB)
+    datasets_db.insert({
+        "components": ["A", "B"], "phases": ["ALPHA"], "output": "HM_MIX",
+        "solver": {"mode": "manual", "sublattice_site_ratios": [1],
+                   "sublattice_configurations": [[["A", "B"]], [["A", "B"]]],
+                   "sublattice_occupancies": [[[0.5, 0.5]], [[0.2, 0.8]]]},
+        "conditions": {"P": 101325, "T": 600}, "values": [[[0.0, 0.0]]], "reference": "regular solution",
+    })
+
+    residual_func = FixedConfigurationPropertyResidual(dbf, datasets_db, phase_models=None, symbols_to_fit=['L_ALPHA'])
+
+    # HM_MIX = L x_A x_B for a regular solution
+    residuals, weights = residual_func.get_residuals(np.asarray([2000.0]))
+    assert len(residuals) == len(weights)
+    assert np.allclose(residuals, [500.0, 320.0])
+
+
 def test_get_thermochemical_data_filters_configurations_when_all_configurations_are_invalid(datasets_db):
     datasets_db.insert(CU_MG_HM_MIX_CUMG2_ALL_INVALID)  # No valid configurations
 
@@ -340,6 +359,18 @@ def test_zpf_residual_function(datasets_db):
     assert np.isclose(likelihood, zero_error_prob, rtol=1e-6)
 
 
+def test_zpf_residual_function_without_data(datasets_db):
+    """ZPF residuals are empty without ZPF data"""
+    dbf = Database(CU_MG_TDB)
+
+    residual_func = ZPFResidual(dbf, datasets_db, phase_models=None, symbols_to_fit=[])
+
+    residuals, weights = residual_func.get_residuals(np.asarray([]))
+    assert residuals == []
+    assert weights == []
+    assert residual_func.get_likelihood(np.asarray([])) == 0.0
+
+
 def test_subsystem_zpf_probability(datasets_db):
     """Test binary Cr-Ni data produces the same probability regardless of whether the main system is a binary or ternary."""