diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bb550ca..dfbfd3d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.8', '3.9', '3.10', '3.11']
+        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12']
 
     steps:
       - uses: actions/checkout@v3
diff --git a/src/covjson_pydantic/base_models.py b/src/covjson_pydantic/base_models.py
index 4c1c3eb..b1d2a32 100644
--- a/src/covjson_pydantic/base_models.py
+++ b/src/covjson_pydantic/base_models.py
@@ -1,5 +1,20 @@
+# from typing import Annotated
+import typing
+from typing import TypeVar
+from typing import Union
+
 from pydantic import BaseModel as PydanticBaseModel
 from pydantic import ConfigDict
+from pydantic import Field
+from pydantic.json_schema import SkipJsonSchema
+
+
+# Define an alternative Optional type that doesn't show the None/null value and the default in the schema
+T = TypeVar("T")
+if hasattr(typing, "Annotated"):  # Check if Annotated exists (Python >=3.9)
+    OptionalS = typing.Annotated[Union[T, SkipJsonSchema[None]], Field(json_schema_extra=lambda x: x.pop("default"))]
+else:  # For Python 3.8 we don't support dropping the default value
+    OptionalS = Union[T, SkipJsonSchema[None]]  # type: ignore
 
 
 class CovJsonBaseModel(PydanticBaseModel):
diff --git a/src/covjson_pydantic/coverage.py b/src/covjson_pydantic/coverage.py
index 279240b..f25bcab 100644
--- a/src/covjson_pydantic/coverage.py
+++ b/src/covjson_pydantic/coverage.py
@@ -1,12 +1,12 @@
 from typing import Dict
 from typing import List
 from typing import Literal
-from typing import Optional
 from typing import Union
 
 from pydantic import AnyUrl
 
 from .base_models import CovJsonBaseModel
+from .base_models import OptionalS
 from .domain import Domain
 from .domain import DomainType
 from .ndarray import NdArray
@@ -17,18 +17,18 @@
 
 
 class Coverage(CovJsonBaseModel, extra="allow"):
-    id: Optional[str] = None
+    id: OptionalS[str] = None
     type: Literal["Coverage"] = "Coverage"
     domain: Domain
-    parameters: Optional[Dict[str, Parameter]] = None
-    parameterGroups: Optional[List[ParameterGroup]] = None  # noqa: N815
+    parameters: OptionalS[Dict[str, Parameter]] = None
+    parameterGroups: OptionalS[List[ParameterGroup]] = None  # noqa: N815
     ranges: Dict[str, Union[NdArray, TiledNdArray, AnyUrl]]
 
 
 class CoverageCollection(CovJsonBaseModel, extra="allow"):
     type: Literal["CoverageCollection"] = "CoverageCollection"
-    domainType: Optional[DomainType] = None  # noqa: N815
+    domainType: OptionalS[DomainType] = None  # noqa: N815
     coverages: List[Coverage]
-    parameters: Optional[Dict[str, Parameter]] = None
-    parameterGroups: Optional[List[ParameterGroup]] = None  # noqa: N815
-    referencing: Optional[List[ReferenceSystemConnectionObject]] = None
+    parameters: OptionalS[Dict[str, Parameter]] = None
+    parameterGroups: OptionalS[List[ParameterGroup]] = None  # noqa: N815
+    referencing: OptionalS[List[ReferenceSystemConnectionObject]] = None
diff --git a/src/covjson_pydantic/domain.py b/src/covjson_pydantic/domain.py
index 61dfdfb..b5fc3c3 100644
--- a/src/covjson_pydantic/domain.py
+++ b/src/covjson_pydantic/domain.py
@@ -2,7 +2,6 @@
 from typing import Generic
 from typing import List
 from typing import Literal
-from typing import Optional
 from typing import Tuple
 from typing import TypeVar
 from typing import Union
@@ -13,6 +12,7 @@
 from pydantic import PositiveInt
 
 from .base_models import CovJsonBaseModel
+from .base_models import OptionalS
 from .reference_system import ReferenceSystemConnectionObject
 
 
@@ -34,10 +34,10 @@ def single_value_case(self):
 # Combination between Generics (ValuesT) and datetime and strict mode causes issues between JSON <-> Pydantic
 # conversions. Strict mode has been disabled. Issue: https://github.com/KNMI/covjson-pydantic/issues/4
 class ValuesAxis(CovJsonBaseModel, Generic[ValuesT], extra="allow", strict=False):
-    dataType: Optional[str] = None  # noqa: N815
-    coordinates: Optional[List[str]] = None
+    dataType: OptionalS[str] = None  # noqa: N815
+    coordinates: OptionalS[List[str]] = None
     values: List[ValuesT]
-    bounds: Optional[List[ValuesT]] = None
+    bounds: OptionalS[List[ValuesT]] = None
 
     @model_validator(mode="after")
     def bounds_length(self):
@@ -56,11 +56,11 @@ class DomainType(str, Enum):
 
 
 class Axes(CovJsonBaseModel):
-    x: Optional[Union[ValuesAxis[float], CompactAxis]] = None
-    y: Optional[Union[ValuesAxis[float], CompactAxis]] = None
-    z: Optional[Union[ValuesAxis[float], CompactAxis]] = None
-    t: Optional[ValuesAxis[AwareDatetime]] = None
-    composite: Optional[ValuesAxis[Tuple]] = None
+    x: OptionalS[Union[ValuesAxis[float], CompactAxis]] = None
+    y: OptionalS[Union[ValuesAxis[float], CompactAxis]] = None
+    z: OptionalS[Union[ValuesAxis[float], CompactAxis]] = None
+    t: OptionalS[ValuesAxis[AwareDatetime]] = None
+    composite: OptionalS[ValuesAxis[Tuple]] = None
 
     @model_validator(mode="after")
     def at_least_one_axes(self):
@@ -71,9 +71,9 @@ def at_least_one_axes(self):
 
 class Domain(CovJsonBaseModel, extra="allow"):
     type: Literal["Domain"] = "Domain"
-    domainType: Optional[DomainType] = None  # noqa: N815
+    domainType: OptionalS[DomainType] = None  # noqa: N815
     axes: Axes
-    referencing: Optional[List[ReferenceSystemConnectionObject]] = None
+    referencing: OptionalS[List[ReferenceSystemConnectionObject]] = None
 
     # TODO: This is a workaround to allow domainType to work in strict mode, in combination with FastAPI.
     # See: https://github.com/tiangolo/fastapi/discussions/9868
diff --git a/src/covjson_pydantic/ndarray.py b/src/covjson_pydantic/ndarray.py
index abda788..5321563 100644
--- a/src/covjson_pydantic/ndarray.py
+++ b/src/covjson_pydantic/ndarray.py
@@ -7,6 +7,7 @@
 from pydantic import model_validator
 
 from .base_models import CovJsonBaseModel
+from .base_models import OptionalS
 
 
 # TODO: Support for integers and strings
@@ -17,8 +18,8 @@ class DataType(str, Enum):
 class NdArray(CovJsonBaseModel, extra="allow"):
     type: Literal["NdArray"] = "NdArray"
     dataType: DataType = DataType.float  # noqa: N815
-    axisNames: Optional[List[str]] = None  # noqa: N815
-    shape: Optional[List[int]] = None
+    axisNames: OptionalS[List[str]] = None  # noqa: N815
+    shape: OptionalS[List[int]] = None
     values: List[Optional[float]]
 
     @model_validator(mode="after")
diff --git a/src/covjson_pydantic/observed_property.py b/src/covjson_pydantic/observed_property.py
index 976a067..461326e 100644
--- a/src/covjson_pydantic/observed_property.py
+++ b/src/covjson_pydantic/observed_property.py
@@ -1,18 +1,18 @@
 from typing import List
-from typing import Optional
 
 from .base_models import CovJsonBaseModel
+from .base_models import OptionalS
 from .i18n import i18n
 
 
 class Category(CovJsonBaseModel):
     id: str
     label: i18n
-    description: Optional[i18n] = None
+    description: OptionalS[i18n] = None
 
 
 class ObservedProperty(CovJsonBaseModel):
-    id: Optional[str] = None
+    id: OptionalS[str] = None
     label: i18n
-    description: Optional[i18n] = None
-    categories: Optional[List[Category]] = None
+    description: OptionalS[i18n] = None
+    categories: OptionalS[List[Category]] = None
diff --git a/src/covjson_pydantic/parameter.py b/src/covjson_pydantic/parameter.py
index 9f684cc..69df921 100644
--- a/src/covjson_pydantic/parameter.py
+++ b/src/covjson_pydantic/parameter.py
@@ -1,12 +1,12 @@
 from typing import Dict
 from typing import List
 from typing import Literal
-from typing import Optional
 from typing import Union
 
 from pydantic import model_validator
 
 from .base_models import CovJsonBaseModel
+from .base_models import OptionalS
 from .i18n import i18n
 from .observed_property import ObservedProperty
 from .unit import Unit
@@ -14,12 +14,12 @@
 
 class Parameter(CovJsonBaseModel, extra="allow"):
     type: Literal["Parameter"] = "Parameter"
-    id: Optional[str] = None
-    label: Optional[i18n] = None
-    description: Optional[i18n] = None
+    id: OptionalS[str] = None
+    label: OptionalS[i18n] = None
+    description: OptionalS[i18n] = None
     observedProperty: ObservedProperty  # noqa: N815
-    categoryEncoding: Optional[Dict[str, Union[int, List[int]]]] = None  # noqa: N815
-    unit: Optional[Unit] = None
+    categoryEncoding: OptionalS[Dict[str, Union[int, List[int]]]] = None  # noqa: N815
+    unit: OptionalS[Unit] = None
 
     @model_validator(mode="after")
     def must_not_have_unit_if_observed_property_has_categories(self):
@@ -34,10 +34,10 @@ def must_not_have_unit_if_observed_property_has_categories(self):
 
 class ParameterGroup(CovJsonBaseModel, extra="allow"):
     type: Literal["ParameterGroup"] = "ParameterGroup"
-    id: Optional[str] = None
-    label: Optional[i18n] = None
-    description: Optional[i18n] = None
-    observedProperty: Optional[ObservedProperty] = None  # noqa: N815
+    id: OptionalS[str] = None
+    label: OptionalS[i18n] = None
+    description: OptionalS[i18n] = None
+    observedProperty: OptionalS[ObservedProperty] = None  # noqa: N815
     members: List[str]
 
     @model_validator(mode="after")
diff --git a/src/covjson_pydantic/reference_system.py b/src/covjson_pydantic/reference_system.py
index 7222330..1ca7adc 100644
--- a/src/covjson_pydantic/reference_system.py
+++ b/src/covjson_pydantic/reference_system.py
@@ -1,35 +1,35 @@
 from typing import Dict
 from typing import List
 from typing import Literal
-from typing import Optional
 from typing import Union
 
 from pydantic import AnyUrl
 from pydantic import model_validator
 
 from .base_models import CovJsonBaseModel
+from .base_models import OptionalS
 from .i18n import i18n
 
 
 class TargetConcept(CovJsonBaseModel):
-    id: Optional[str] = None  # Not in spec, but needed for example in spec for 'Identifier-based Reference Systems'
+    id: OptionalS[str] = None  # Not in spec, but needed for example in spec for 'Identifier-based Reference Systems'
     label: i18n
-    description: Optional[i18n] = None
+    description: OptionalS[i18n] = None
 
 
 class ReferenceSystem(CovJsonBaseModel, extra="allow"):
     type: Literal["GeographicCRS", "ProjectedCRS", "VerticalCRS", "TemporalRS", "IdentifierRS"]
-    id: Optional[str] = None
-    description: Optional[i18n] = None
+    id: OptionalS[str] = None
+    description: OptionalS[i18n] = None
 
     # Only for TemporalRS
-    calendar: Optional[Union[Literal["Gregorian"], AnyUrl]] = None
-    timeScale: Optional[AnyUrl] = None  # noqa: N815
+    calendar: OptionalS[Union[Literal["Gregorian"], AnyUrl]] = None
+    timeScale: OptionalS[AnyUrl] = None  # noqa: N815
 
     # Only for IdentifierRS
-    label: Optional[i18n] = None
-    targetConcept: Optional[TargetConcept] = None  # noqa: N815
-    identifiers: Optional[Dict[str, TargetConcept]] = None
+    label: OptionalS[i18n] = None
+    targetConcept: OptionalS[TargetConcept] = None  # noqa: N815
+    identifiers: OptionalS[Dict[str, TargetConcept]] = None
 
     @model_validator(mode="after")
     def check_type_specific_fields(self):
diff --git a/src/covjson_pydantic/unit.py b/src/covjson_pydantic/unit.py
index f1783dd..d2edda4 100644
--- a/src/covjson_pydantic/unit.py
+++ b/src/covjson_pydantic/unit.py
@@ -1,9 +1,9 @@
-from typing import Optional
 from typing import Union
 
 from pydantic import model_validator
 
 from .base_models import CovJsonBaseModel
+from .base_models import OptionalS
 from .i18n import i18n
 
 
@@ -13,9 +13,9 @@ class Symbol(CovJsonBaseModel):
 
 
 class Unit(CovJsonBaseModel):
-    id: Optional[str] = None
-    label: Optional[i18n] = None
-    symbol: Optional[Union[str, Symbol]] = None
+    id: OptionalS[str] = None
+    label: OptionalS[i18n] = None
+    symbol: OptionalS[Union[str, Symbol]] = None
 
     @model_validator(mode="after")
     def check_either_label_or_symbol(self):