diff --git a/CHANGELOG.md b/CHANGELOG.md
index 311b4b60..baabd64f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - Add support for remote references to a file at a URL.
 - Add support for default values.
+- Add check for whether the value of an extension property is null.
 
 ## Version 0.14.0 - 2020-02-21
 
diff --git a/open_alchemy/helpers/get_ext_prop/__init__.py b/open_alchemy/helpers/get_ext_prop/__init__.py
index 3b694993..d254a3c3 100644
--- a/open_alchemy/helpers/get_ext_prop/__init__.py
+++ b/open_alchemy/helpers/get_ext_prop/__init__.py
@@ -45,9 +45,16 @@ def get_ext_prop(
         The value of the property or the default value if it does not exist.
 
     """
+    # Check for presence of name
+    if name not in source:
+        return default
+
+    # Retrieve value
     value = source.get(name)
     if value is None:
-        return default
+        raise exceptions.MalformedExtensionPropertyError(
+            f"The value of the {name} extension property cannot be null."
+        )
 
     schema = _SCHEMAS.get(name)
     try:

Examine nullability of extension properties
Examine whether nullability of extension properties is a problem sine JSON schema does not support _nullable_.
diff --git a/tests/open_alchemy/helpers/test_get_ext_prop.py b/tests/open_alchemy/helpers/test_get_ext_prop.py
index 6f78bf2d..c781c417 100644
--- a/tests/open_alchemy/helpers/test_get_ext_prop.py
+++ b/tests/open_alchemy/helpers/test_get_ext_prop.py
@@ -44,6 +44,7 @@ def test_miss_default():
         ("x-foreign-key", "no column"),
         ("x-foreign-key-column", True),
         ("x-tablename", True),
+        ("x-tablename", None),
         ("x-de-$ref", True),
         ("x-dict-ignore", "True"),
         ("x-generated", "True"),
@@ -60,6 +61,7 @@ def test_miss_default():
         "x-foreign-key invalid format",
         "x-foreign-key-column",
         "x-tablename",
+        "x-tablename None",
         "x-de-$ref",
         "x-dict-ignore",
         "x-generated",
diff --git a/tests/open_alchemy/test_model_factory.py b/tests/open_alchemy/test_model_factory.py
index f9031c15..a0ef659e 100644
--- a/tests/open_alchemy/test_model_factory.py
+++ b/tests/open_alchemy/test_model_factory.py
@@ -36,6 +36,27 @@ def test_missing_tablename():
         )
 
 
+@pytest.mark.model
+def test_tablename_none():
+    """
+    GIVEN schemas with schema that has None for the tablename
+    WHEN model_factory is called with the name of the schema
+    THEN MalformedExtensionPropertyError is raised.
+    """
+    with pytest.raises(exceptions.MalformedExtensionPropertyError):
+        model_factory.model_factory(
+            name="SingleProperty",
+            base=mock.MagicMock,
+            schemas={
+                "SingleProperty": {
+                    "x-tablename": None,
+                    "type": "object",
+                    "properties": {"property_1": {"type": "integer"}},
+                }
+            },
+        )
+
+
 @pytest.mark.model
 def test_not_object():
     """

pip install -e .[dev,test]
parse_log_pytest
requirements.txt
pytest pytest-cov
3.8.0
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
alabaster==0.7.13
alembic==1.14.1
anyio==4.5.2
asgiref==3.8.1
astroid==3.2.4
attrs==25.3.0
babel==2.17.0
bandit==1.7.10
black==24.8.0
blinker==1.8.2
cachetools==5.5.2
certifi==2025.1.31
cfgv==3.4.0
chardet==5.2.0
charset-normalizer==3.4.1
click==8.1.8
colorama==0.4.6
connexion==3.2.0
coverage==7.6.1
dill==0.3.9
distlib==0.3.9
doc8==1.1.2
docutils==0.20.1
exceptiongroup==1.2.2
filelock==3.16.1
flake8==5.0.4
Flask==3.0.3
Flask-SQLAlchemy==3.1.1
greenlet==3.1.1
h11==0.14.0
httpcore==1.0.7
httpx==0.28.1
identify==2.6.1
idna==3.10
imagesize==1.4.1
importlib-resources==5.13.0
importlib_metadata==8.5.0
inflection==0.5.1
iniconfig==2.1.0
isort==5.13.2
itsdangerous==2.2.0
Jinja2==3.1.6
jsonschema==4.23.0
jsonschema-specifications==2023.12.1
Mako==1.3.9
markdown-it-py==3.0.0
MarkupSafe==2.1.5
mccabe==0.7.0
mdurl==0.1.2
mypy==1.14.1
mypy-extensions==1.0.0
nodeenv==1.9.1
-e git+https://github.com/jdkandersson/OpenAlchemy.git@123cc73aecfe79cd6bc46d829d388917c9df9e43#egg=OpenAlchemy
packaging==24.2
pathspec==0.12.1
pbr==6.1.1
pkgutil_resolve_name==1.3.10
platformdirs==4.3.6
pluggy==1.5.0
pre-commit==3.5.0
pycodestyle==2.9.1
pydocstyle==6.3.0
pyflakes==2.5.0
Pygments==2.19.1
pylint==3.2.7
pyproject-api==1.8.0
pytest==8.3.5
pytest-bandit==0.6.1
pytest-cov==5.0.0
pytest-flake8==1.2.2
pytest-flask==1.3.0
pytest-flask-sqlalchemy==1.1.0
pytest-mock==3.14.0
pytest-randomly==3.15.0
python-multipart==0.0.20
pytz==2025.2
PyYAML==6.0.2
referencing==0.35.1
requests==2.32.3
restructuredtext_lint==1.4.0
rich==14.0.0
rpds-py==0.20.1
sniffio==1.3.1
snowballstemmer==2.2.0
Sphinx==7.1.2
sphinxcontrib-applehelp==1.0.4
sphinxcontrib-devhelp==1.0.2
sphinxcontrib-htmlhelp==2.0.1
sphinxcontrib-jsmath==1.0.1
sphinxcontrib-qthelp==1.0.3
sphinxcontrib-serializinghtml==1.1.5
SQLAlchemy==2.0.40
starlette==0.44.0
stevedore==5.3.0
swagger_ui_bundle==1.1.0
tomli==2.2.1
tomlkit==0.13.2
tox==4.25.0
tox-pyenv==1.1.0
typeguard==4.4.0
typing_extensions==4.13.0
urllib3==2.2.3
virtualenv==20.29.3
Werkzeug==3.0.6
zipp==3.20.2

name: OpenAlchemy
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - libedit=3.1.20230828=h5eee18b_0
  - libffi=3.2.1=hf484d3e_1007
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=24.2=py38h06a4308_0
  - python=3.8.0=h0371630_2
  - readline=7.0=h7b6447c_5
  - setuptools=75.1.0=py38h06a4308_0
  - sqlite=3.33.0=h62c20be_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.44.0=py38h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - alabaster==0.7.13
      - alembic==1.14.1
      - anyio==4.5.2
      - asgiref==3.8.1
      - astroid==3.2.4
      - attrs==25.3.0
      - babel==2.17.0
      - bandit==1.7.10
      - black==24.8.0
      - blinker==1.8.2
      - cachetools==5.5.2
      - certifi==2025.1.31
      - cfgv==3.4.0
      - chardet==5.2.0
      - charset-normalizer==3.4.1
      - click==8.1.8
      - colorama==0.4.6
      - connexion==3.2.0
      - coverage==7.6.1
      - dill==0.3.9
      - distlib==0.3.9
      - doc8==1.1.2
      - docutils==0.20.1
      - exceptiongroup==1.2.2
      - filelock==3.16.1
      - flake8==5.0.4
      - flask==3.0.3
      - flask-sqlalchemy==3.1.1
      - greenlet==3.1.1
      - h11==0.14.0
      - httpcore==1.0.7
      - httpx==0.28.1
      - identify==2.6.1
      - idna==3.10
      - imagesize==1.4.1
      - importlib-metadata==8.5.0
      - importlib-resources==5.13.0
      - inflection==0.5.1
      - iniconfig==2.1.0
      - isort==5.13.2
      - itsdangerous==2.2.0
      - jinja2==3.1.6
      - jsonschema==4.23.0
      - jsonschema-specifications==2023.12.1
      - mako==1.3.9
      - markdown-it-py==3.0.0
      - markupsafe==2.1.5
      - mccabe==0.7.0
      - mdurl==0.1.2
      - mypy==1.14.1
      - mypy-extensions==1.0.0
      - nodeenv==1.9.1
      - packaging==24.2
      - pathspec==0.12.1
      - pbr==6.1.1
      - pkgutil-resolve-name==1.3.10
      - platformdirs==4.3.6
      - pluggy==1.5.0
      - pre-commit==3.5.0
      - pycodestyle==2.9.1
      - pydocstyle==6.3.0
      - pyflakes==2.5.0
      - pygments==2.19.1
      - pylint==3.2.7
      - pyproject-api==1.8.0
      - pytest==8.3.5
      - pytest-bandit==0.6.1
      - pytest-cov==5.0.0
      - pytest-flake8==1.2.2
      - pytest-flask==1.3.0
      - pytest-flask-sqlalchemy==1.1.0
      - pytest-mock==3.14.0
      - pytest-randomly==3.15.0
      - python-multipart==0.0.20
      - pytz==2025.2
      - pyyaml==6.0.2
      - referencing==0.35.1
      - requests==2.32.3
      - restructuredtext-lint==1.4.0
      - rich==14.0.0
      - rpds-py==0.20.1
      - sniffio==1.3.1
      - snowballstemmer==2.2.0
      - sphinx==7.1.2
      - sphinxcontrib-applehelp==1.0.4
      - sphinxcontrib-devhelp==1.0.2
      - sphinxcontrib-htmlhelp==2.0.1
      - sphinxcontrib-jsmath==1.0.1
      - sphinxcontrib-qthelp==1.0.3
      - sphinxcontrib-serializinghtml==1.1.5
      - sqlalchemy==2.0.40
      - starlette==0.44.0
      - stevedore==5.3.0
      - swagger-ui-bundle==1.1.0
      - tomli==2.2.1
      - tomlkit==0.13.2
      - tox==4.25.0
      - tox-pyenv==1.1.0
      - typeguard==4.4.0
      - typing-extensions==4.13.0
      - urllib3==2.2.3
      - virtualenv==20.29.3
      - werkzeug==3.0.6
      - zipp==3.20.2
prefix: /opt/conda/envs/OpenAlchemy

tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-tablename tests/open_alchemy/test_model_factory.py::test_tablename_none
tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-foreign-key-column] tests/open_alchemy/helpers/test_get_ext_prop.py::test_miss_default tests/open_alchemy/helpers/test_get_ext_prop.py::test_composite_index_invalid[empty tests/open_alchemy/helpers/test_get_ext_prop.py::test_composite_index_invalid[object tests/open_alchemy/helpers/test_get_ext_prop.py::test_relationship_backrefs_valid[empty] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-unique] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-backref] tests/open_alchemy/helpers/test_get_ext_prop.py::test_relationship_backrefs_invalid[object tests/open_alchemy/helpers/test_get_ext_prop.py::test_relationship_backrefs_valid[single tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-uselist] tests/open_alchemy/helpers/test_get_ext_prop.py::test_unique_constraint_invalid[object tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-autoincrement] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-de-$ref] tests/open_alchemy/helpers/test_get_ext_prop.py::test_unique_constraint_invalid[list tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-primary-key] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-index] tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-tablename] tests/open_alchemy/helpers/test_get_ext_prop.py::test_composite_index_valid[list tests/open_alchemy/helpers/test_get_ext_prop.py::test_unique_constraint_invalid[empty tests/open_alchemy/helpers/test_get_ext_prop.py::test_unique_constraint_valid[list tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-primary-key] tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-foreign-key tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-backref] tests/open_alchemy/helpers/test_get_ext_prop.py::test_relationship_backrefs_valid[multiple] tests/open_alchemy/helpers/test_get_ext_prop.py::test_composite_index_valid[object tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-unique] tests/open_alchemy/helpers/test_get_ext_prop.py::test_unique_constraint_valid[object tests/open_alchemy/helpers/test_get_ext_prop.py::test_composite_index_invalid[not tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-autoincrement] tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-uselist] tests/open_alchemy/helpers/test_get_ext_prop.py::test_composite_index_invalid[list tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-de-$ref] tests/open_alchemy/helpers/test_get_ext_prop.py::test_composite_index_valid[object] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-tablename] tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-index] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-generated] tests/open_alchemy/helpers/test_get_ext_prop.py::test_miss tests/open_alchemy/helpers/test_get_ext_prop.py::test_pop tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-generated] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-foreign-key-column] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-dict-ignore] tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-dict-ignore] tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-foreign-key] tests/open_alchemy/helpers/test_get_ext_prop.py::test_invalid[x-secondary] tests/open_alchemy/helpers/test_get_ext_prop.py::test_unique_constraint_invalid[not tests/open_alchemy/helpers/test_get_ext_prop.py::test_relationship_backrefs_invalid[not tests/open_alchemy/helpers/test_get_ext_prop.py::test_valid[x-secondary] tests/open_alchemy/helpers/test_get_ext_prop.py::flake-8::FLAKE8 tests/open_alchemy/test_model_factory.py::flake-8::FLAKE8 tests/open_alchemy/test_model_factory.py::test_schema[multiple tests/open_alchemy/test_model_factory.py::test_schema[single tests/open_alchemy/test_model_factory.py::test_properties_missing tests/open_alchemy/test_model_factory.py::test_missing_tablename tests/open_alchemy/test_model_factory.py::test_missing_schema tests/open_alchemy/test_model_factory.py::test_ref tests/open_alchemy/test_model_factory.py::test_single_property_required tests/open_alchemy/test_model_factory.py::test_properties_empty tests/open_alchemy/test_model_factory.py::test_multiple_property tests/open_alchemy/test_model_factory.py::test_tablename tests/open_alchemy/test_model_factory.py::test_all_of tests/open_alchemy/test_model_factory.py::test_single_property tests/open_alchemy/test_model_factory.py::test_table_args_unique tests/open_alchemy/test_model_factory.py::test_not_object tests/open_alchemy/test_model_factory.py::test_single_property_required_missing tests/open_alchemy/test_model_factory.py::test_single_property_not_required tests/open_alchemy/test_model_factory.py::test_schema_relationship_invalid tests/open_alchemy/test_model_factory.py::test_table_args_index
open_alchemy/helpers/get_ext_prop/__init__.py CHANGELOG.md
open_alchemy/helpers/get_ext_prop/__init__.py CHANGELOG.md