diff --git a/src/aiida_pyscf/calculations/base.py b/src/aiida_pyscf/calculations/base.py
index e2e8cde..573d4e4 100644
--- a/src/aiida_pyscf/calculations/base.py
+++ b/src/aiida_pyscf/calculations/base.py
@@ -2,7 +2,6 @@
 """``CalcJob`` plugin for PySCF."""
 from __future__ import annotations
 
-import copy
 import io
 import numbers
 import pathlib
@@ -130,15 +129,23 @@ def define(cls, spec: CalcJobProcessSpec):  # type: ignore[override]
         )
 
     @classmethod
-    def validate_parameters(cls, value: Dict | None, _) -> str | None:  # noqa: PLR0911, PLR0912
+    def get_valid_parameter_keys(cls) -> tuple[str, ...]:
+        """Return list of valid keys for the ``parameters`` input."""
+        return ('mean_field', 'localize_orbitals', 'optimizer', 'cubegen', 'fcidump', 'hessian', 'results', 'structure')
+
+    @classmethod
+    def validate_parameters(cls, parameters: Dict | None, _) -> str | None:  # noqa: PLR0911, PLR0912
         """Validate the parameters input."""
-        if not value:
+        if not parameters:
             return None
 
-        parameters = copy.deepcopy(value.get_dict())
+        unsupported_keys = set(parameters.keys()).difference(set(cls.get_valid_parameter_keys()))
+
+        if unsupported_keys:
+            return f'The following arguments are not supported: {", ".join(unsupported_keys)}'
 
-        mean_field = parameters.pop('mean_field', {})
-        mean_field_method = mean_field.pop('method', None)
+        mean_field = parameters.get('mean_field', {})
+        mean_field_method = mean_field.get('method')
         valid_methods = ['RKS', 'RHF', 'DKS', 'DHF', 'GKS', 'GHF', 'HF', 'KS', 'ROHF', 'ROKS', 'UKS', 'UHF']
         options = ' '.join(valid_methods)
 
@@ -154,7 +161,7 @@ def validate_parameters(cls, value: Dict | None, _) -> str | None:  # noqa: PLR0
                 'plugin if the `checkpoint` input is provided.'
             )
 
-        if (localize_orbitals := parameters.pop('localize_orbitals', None)) is not None:
+        if (localize_orbitals := parameters.get('localize_orbitals')) is not None:
             valid_lo = ('boys', 'cholesky', 'edmiston', 'iao', 'ibo', 'lowdin', 'nao', 'orth', 'pipek', 'vvo')
             method = localize_orbitals.get('method')
             if method is None:
@@ -163,7 +170,7 @@ def validate_parameters(cls, value: Dict | None, _) -> str | None:  # noqa: PLR0
             if method.lower() not in valid_lo:
                 return f'Invalid method `{method}` specified in `localize_orbitals` parameters. Choose from: {valid_lo}'
 
-        if (optimizer := parameters.pop('optimizer', None)) is not None:
+        if (optimizer := parameters.get('optimizer')) is not None:
             valid_solvers = ('geometric', 'berny')
             solver = optimizer.get('solver')
 
@@ -173,7 +180,7 @@ def validate_parameters(cls, value: Dict | None, _) -> str | None:  # noqa: PLR0
             if solver.lower() not in valid_solvers:
                 return f'Invalid solver `{solver}` specified in `optimizer` parameters. Choose from: {valid_solvers}'
 
-        if (cubegen := parameters.pop('cubegen', None)) is not None:
+        if (cubegen := parameters.get('cubegen')) is not None:
             orbitals = cubegen.get('orbitals')
             indices = orbitals.get('indices') if orbitals is not None else None
 
@@ -186,7 +193,7 @@ def validate_parameters(cls, value: Dict | None, _) -> str | None:  # noqa: PLR0
             if indices is not None and (not isinstance(indices, list) or any(not isinstance(e, int) for e in indices)):
                 return f'The `cubegen.orbitals.indices` parameter should be a list of integers, but got: {indices}'
 
-        if (fcidump := parameters.pop('fcidump', None)) is not None:
+        if (fcidump := parameters.get('fcidump')) is not None:
             active_spaces = fcidump.get('active_spaces')
             occupations = fcidump.get('occupations')
             arrays = []
@@ -205,13 +212,6 @@ def validate_parameters(cls, value: Dict | None, _) -> str | None:  # noqa: PLR0
             if arrays[0].shape != arrays[1].shape:
                 return 'The `fcipdump.active_spaces` and `fcipdump.occupations` arrays have different shapes.'
 
-        # Remove other known arguments
-        for key in ('hessian', 'results', 'structure'):
-            parameters.pop(key, None)
-
-        if unknown_keys := list(parameters.keys()):
-            return f'The following arguments are not supported: {", ".join(unknown_keys)}'
-
     def get_template_environment(self) -> Environment:
         """Return the template environment that should be used for rendering.