diff --git a/src/nomad_simulations/schema_packages/properties/greens_function.py b/src/nomad_simulations/schema_packages/properties/greens_function.py
index 967fa1ab..c4788c7e 100644
--- a/src/nomad_simulations/schema_packages/properties/greens_function.py
+++ b/src/nomad_simulations/schema_packages/properties/greens_function.py
@@ -173,14 +173,17 @@ def find_space_id(space_map: dict) -> str:
             return ''
 
         space_id = find_space_id(_real_space_map) + find_space_id(_time_space_map)
-        return space_id
+        return space_id if space_id else None
 
     def normalize(self, archive: 'EntryArchive', logger: 'BoundLogger') -> None:
         super().normalize(archive, logger)
 
-        if not self.space_id:
-            self.space_id = self.resolve_space_id()
-
+        space_id = self.resolve_space_id()
+        if (self.space_id is not None and self.space_id != space_id):
+            logger.warning(
+                f'The stored `space_id`, {self.space_id}, does not coincide with the resolved one, {space_id}. We will update it.'
+            )
+        self.space_id = space_id
 
 class ElectronicGreensFunction(BaseGreensFunction):
     """
@@ -365,7 +368,7 @@ def resolve_system_correlation_strengths(self) -> str:
             return 'OSMI'
         elif np.all(self.value < 1e-2):
             return 'Mott insulator'
-        return ''
+        return None
 
     def normalize(self, archive: 'EntryArchive', logger: 'BoundLogger') -> None:
         super().normalize(archive, logger)
@@ -376,5 +379,9 @@ def normalize(self, archive: 'EntryArchive', logger: 'BoundLogger') -> None:
             )
             return
 
-        if not self.system_correlation_strengths:
-            self.system_correlation_strengths = self.resolve_system_correlation_strengths()
+        system_correlation_strengths = self.resolve_system_correlation_strengths()
+        if (self.system_correlation_strengths is not None and self.system_correlation_strengths != system_correlation_strengths):
+            logger.warning(
+                f'The stored `system_correlation_strengths`, {self.system_correlation_strengths}, does not coincide with the resolved one, {system_correlation_strengths}. We will update it.'
+            )
+        self.system_correlation_strengths = system_correlation_strengths
diff --git a/tests/test_greens_function.py b/tests/test_greens_function.py
index 25c8b208..1cac4038 100644
--- a/tests/test_greens_function.py
+++ b/tests/test_greens_function.py
@@ -16,14 +16,12 @@
 # limitations under the License.
 #
 
-from typing import Optional, Union
+from typing import Union, Optional
 
 import pytest
 
+from nomad.datamodel import EntryArchive
 from nomad_simulations.schema_packages.properties import (
-    ElectronicGreensFunction,
-    ElectronicSelfEnergy,
-    HybridizationFunction,
     QuasiparticleWeight,
 )
 from nomad_simulations.schema_packages.properties.greens_function import (
@@ -38,6 +36,8 @@
     WignerSeitz,
 )
 
+from . import logger
+
 
 class TestBaseGreensFunction:
     """
@@ -47,7 +47,7 @@ class TestBaseGreensFunction:
     @pytest.mark.parametrize(
         'variables, result',
         [
-            ([], ''),
+            ([], None),
             ([WignerSeitz()], 'r'),
             ([KMesh()], 'k'),
             ([Time()], 't'),
@@ -72,6 +72,38 @@ def test_resolve_space_id(self, variables: list[Union[WignerSeitz, KMesh, Time,
         gfs.variables = variables
         assert gfs.resolve_space_id() == result
 
+    @pytest.mark.parametrize(
+        'space_id, variables, result',
+        [
+            ('', [], None),  # empty `space_id`
+            ('rt', [], None),  # `space_id` set by parser
+            ('', [WignerSeitz()], 'r'),  # resolving `space_id`
+            ('rt', [WignerSeitz()], 'r'),  # normalize overwrites `space_id`
+            ('', [KMesh()], 'k'),
+            ('', [Time()], 't'),
+            ('', [ImaginaryTime()], 'it'),
+            ('', [Frequency()], 'w'),
+            ('', [MatsubaraFrequency()], 'iw'),
+            ('', [WignerSeitz(), Time()], 'rt'),
+            ('', [WignerSeitz(), ImaginaryTime()], 'rit'),
+            ('', [WignerSeitz(), Frequency()], 'rw'),
+            ('', [WignerSeitz(), MatsubaraFrequency()], 'riw'),
+            ('', [KMesh(), Time()], 'kt'),
+            ('', [KMesh(), ImaginaryTime()], 'kit'),
+            ('', [KMesh(), Frequency()], 'kw'),
+            ('', [KMesh(), MatsubaraFrequency()], 'kiw'),
+        ],
+    )
+    def test_normalize(self, space_id: str, variables: list[Union[WignerSeitz, KMesh, Time, ImaginaryTime, Frequency, MatsubaraFrequency]], result: Optional[str]):
+        """
+        Test the `normalize` method of the `BaseGreensFunction` class.
+        """
+        gfs = BaseGreensFunction(n_atoms=1, n_correlated_orbitals=1)
+        gfs.variables = variables
+        gfs.space_id = space_id if space_id else None
+        gfs.normalize(archive=EntryArchive(), logger=logger)
+        assert gfs.space_id == result
+
 
 
 class TestQuasiparticleWeight:
@@ -103,13 +135,34 @@ def test_is_valid_quasiparticle_weight(self, value: list[float], result: bool):
             ([[0.2, 0.3, 0.1]], 'strongly-correlated metal'),
             ([[0, 0.3, 0.1]], 'OSMI'),
             ([[0, 0, 0]], 'Mott insulator'),
-            ([[1.0, 0.8, 0.2]], ''),
+            ([[1.0, 0.8, 0.2]], None),
         ],
     )
-    def test_resolve_system_correlation_strengths(self, value: list[float], result: str):
+    def test_resolve_system_correlation_strengths(self, value: list[float], result: Optional[str]):
         """
         Test the `resolve_system_correlation_strengths` method of the `QuasiparticleWeight` class.
         """
         quasiparticle_weight = QuasiparticleWeight(n_atoms=1, n_correlated_orbitals=3)
         quasiparticle_weight.value = value
         assert quasiparticle_weight.resolve_system_correlation_strengths() == result
+
+    @pytest.mark.parametrize(
+        'value, result',
+        [
+            ([[1, 0.5, -2]], None),
+            ([[1, 0.5, 8]], None),
+            ([[1, 0.9, 0.8]], 'non-correlated metal'),
+            ([[0.2, 0.3, 0.1]], 'strongly-correlated metal'),
+            ([[0, 0.3, 0.1]], 'OSMI'),
+            ([[0, 0, 0]], 'Mott insulator'),
+            ([[1.0, 0.8, 0.2]], None),
+        ],
+    )
+    def test_normalize(self, value: list[float], result: Optional[str]):
+        """
+        Test the `normalize` method of the `QuasiparticleWeight` class.
+        """
+        quasiparticle_weight = QuasiparticleWeight(n_atoms=1, n_correlated_orbitals=3)
+        quasiparticle_weight.value = value
+        quasiparticle_weight.normalize(archive=EntryArchive(), logger=logger)
+        assert quasiparticle_weight.system_correlation_strengths == result