diff --git a/.gitignore b/.gitignore
index 4fbf9db..4dc0b15 100644
--- a/.gitignore
+++ b/.gitignore
@@ -93,3 +93,9 @@ ENV/
 
 # PyCharm
 .idea/
+
+# MyPy
+.mypy_cache/
+
+# build output
+dist/
diff --git a/pure_interface.py b/pure_interface.py
index c3d38f8..511959e 100644
--- a/pure_interface.py
+++ b/pure_interface.py
@@ -40,7 +40,7 @@ else:
             super(abstractstaticmethod, self).__init__(callable)
 
 
-__version__ = '3.4.0'
+__version__ = '3.4.1'
 
 
 is_development = not hasattr(sys, 'frozen')
@@ -473,13 +473,13 @@ class PureInterfaceType(abc.ABCMeta):
         * if the type is a concrete class then patch the abstract properties with AttributeProperies.
     """
 
-    def __new__(mcs, clsname, bases, attributes):
+    def __new__(mcs, clsname, bases, attributes, **kwargs):
         # PureInterface is not in globals() when we are constructing the PureInterface class itself.
         has_interface = any(PureInterface in base.mro() for base in bases) if 'PureInterface' in globals() else True
         if not has_interface:
             # Don't interfere if meta class is only included to permit interface inheritance,
             # but no actual interface is being used.
-            cls = super(PureInterfaceType, mcs).__new__(mcs, clsname, bases, attributes)
+            cls = super(PureInterfaceType, mcs).__new__(mcs, clsname, bases, attributes, **kwargs)
             cls._pi = _PIAttributes(False, (), {}, ())
             return cls
 
@@ -546,7 +546,7 @@ class PureInterfaceType(abc.ABCMeta):
                                   'pi_partial_implementation attribute, not it''s value')
 
         # create class
-        cls = super(PureInterfaceType, mcs).__new__(mcs, clsname, bases, namespace)
+        cls = super(PureInterfaceType, mcs).__new__(mcs, clsname, bases, namespace, **kwargs)
         cls._pi = _PIAttributes(type_is_interface, abstract_properties,
                                 interface_method_signatures, interface_attribute_names)
 
diff --git a/setup.py b/setup.py
index d28b81f..1304da6 100644
--- a/setup.py
+++ b/setup.py
@@ -3,7 +3,7 @@ from setuptools import setup
 
 setup(
     name='pure_interface',
-    version='3.4.0',
+    version='3.4.1',
     py_modules=['pure_interface', 'pure_contracts'],
     url='https://github.com/aranzgeo/pure_interface',
     install_requires=['six', 'typing'],

PI does not work with __init_subclass__ with kwargs
See this case for the related ABC change that was made in 3.7: [https://bugs.python.org/issue29581](url)

Since __init_subclass__ landed into 3.6, it's now possible to define classes that support arbitrary keyword arguments in the class definition, like:

`class Foo(Bar, Baz=True):`

However, these kwargs need to be handled by __new__ and passed along (eventually) to init subclass.  Currently classes that are PIType do not support this and give a TypeError on declaration.

Simply patching new to pass the kwargs through seems to do the job:
[pi_kwargs.zip](https://github.com/seequent/pure_interface/files/3105569/pi_kwargs.zip)
diff --git a/tests/test_py3/test_impl3_checks.py b/tests/test_py3/test_impl3_checks.py
index c936bab..12b7404 100644
--- a/tests/test_py3/test_impl3_checks.py
+++ b/tests/test_py3/test_impl3_checks.py
@@ -22,3 +22,16 @@ class TestImplementationChecks(unittest.TestCase):
 
         self.assertIn('a', get_interface_attribute_names(IAnnotation))
         self.assertIn('b', get_interface_attribute_names(IAnnotation))
+
+    def test_works_with_init_subclass_kwargs(self):
+        saved_kwargs = {}
+
+        class ReceivesClassKwargs:
+            def __init_subclass__(cls, **kwargs):
+                super().__init_subclass__()
+                saved_kwargs.update(kwargs)
+
+        class Receiver(ReceivesClassKwargs, PureInterface, x=1, y=2, z=3):
+            pass
+
+        self.assertEqual(saved_kwargs, dict(x=1, y=2, z=3))

pip install -e .[dev]
parse_log_pytest
requirements.txt
pytest
3.6
requirements.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
attrs==22.2.0
certifi==2021.5.30
importlib-metadata==4.8.3
iniconfig==1.1.1
packaging==21.3
pluggy==1.0.0
-e git+https://github.com/seequent/pure_interface.git@d3717fad8acb27d8f71a9fee7d9de798fdee8c16#egg=pure_interface
py==1.11.0
pyparsing==3.1.4
pytest==7.0.1
six==1.17.0
tomli==1.2.3
typing==3.7.4.3
typing_extensions==4.1.1
zipp==3.6.0

name: pure_interface
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
  - certifi=2021.5.30=py36h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - 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=21.2.2=py36h06a4308_0
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - attrs==22.2.0
      - importlib-metadata==4.8.3
      - iniconfig==1.1.1
      - packaging==21.3
      - pluggy==1.0.0
      - py==1.11.0
      - pyparsing==3.1.4
      - pytest==7.0.1
      - six==1.17.0
      - tomli==1.2.3
      - typing==3.7.4.3
      - typing-extensions==4.1.1
      - zipp==3.6.0
prefix: /opt/conda/envs/pure_interface

tests/test_py3/test_impl3_checks.py::TestImplementationChecks::test_works_with_init_subclass_kwargs
tests/test_py3/test_impl3_checks.py::TestImplementationChecks::test_annotations tests/test_py3/test_impl3_checks.py::TestImplementationChecks::test_annotations2
setup.py .gitignore pure_interface.py
setup.py .gitignore pure_interface.py