diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index dba0e19..76a740a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
     steps:
       - uses: actions/checkout@v3
         with:
diff --git a/pyproject.toml b/pyproject.toml
index 269f339..3660e81 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,3 +1,3 @@
 [build-system]
-requires = ["setuptools>=64", "Cython", "oldest-supported-numpy", 'setuptools_scm[toml]>=8']
+requires = ["setuptools>=64", "Cython", "numpy>=1.25", 'setuptools_scm[toml]>=8']
 build-backend = "setuptools.build_meta"
diff --git a/setup.cfg b/setup.cfg
index 2bb8b30..bd67cc0 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -24,11 +24,10 @@ classifiers =
 	Operating System :: OS Independent
 	Programming Language :: Python
 	Programming Language :: Python :: 3
-	Programming Language :: Python :: 3.6
-	Programming Language :: Python :: 3.7
-	Programming Language :: Python :: 3.8
 	Programming Language :: Python :: 3.9
 	Programming Language :: Python :: 3.10
+	Programming Language :: Python :: 3.11
+	Programming Language :: Python :: 3.12
 	Programming Language :: Python :: 3 :: Only
 	Topic :: Scientific/Engineering :: Astronomy
 	Topic :: Scientific/Engineering :: Physics
diff --git a/setup.py b/setup.py
index 7cbd324..281c623 100644
--- a/setup.py
+++ b/setup.py
@@ -1,63 +1,43 @@
-from setuptools import setup
+from setuptools import setup, Extension
 import os
+from Cython.Build import cythonize
+import numpy as np
+
+
+kwargs = dict(
+    include_dirs=[np.get_include()],
+    define_macros=[
+        # fixes a warning when compiling
+        ("NPY_NO_DEPRECATED_API", "NPY_1_7_API_VERSION"),
+        # defines the oldest numpy we want to be compatible with
+        ("NPY_TARGET_VERSION", "NPY_1_21_API_VERSION"),
+    ]
+)
 
-# make sure users without cython can install our extensions
-try:
-    from Cython.Distutils.extension import Extension
-    from Cython.Distutils import build_ext as _build_ext
-    USE_CYTHON = True
-except ImportError:
-    from setuptools import Extension
-    from setuptools.command.build_ext import build_ext as _build_ext
-    USE_CYTHON = False
-
-print('using cython', USE_CYTHON)
-
-
-# make sure numpy is installed before we try to build
-# the extenion
-class build_ext(_build_ext):
-    def finalize_options(self):
-        super().finalize_options()
-        import numpy
-        self.include_dirs.append(numpy.get_include())
-
-
-# if we have cython, use the cython file if not the c file
-ext = '.pyx' if USE_CYTHON else '.c'
 extensions = [
-    Extension('eventio.header', sources=['src/eventio/header' + ext]),
-    Extension('eventio.var_int', sources=['src/eventio/var_int' + ext]),
+    Extension(
+        'eventio.header',
+        sources=['src/eventio/header.pyx'],
+        **kwargs,
+    ),
+    Extension(
+        'eventio.var_int',
+        sources=['src/eventio/var_int.pyx'],
+        **kwargs,
+    ),
     Extension(
         'eventio.simtel.parsing',
-        sources=['src/eventio/simtel/parsing' + ext]
+        sources=['src/eventio/simtel/parsing.pyx'],
+        **kwargs,
     ),
 ]
-cmdclass = {'build_ext': build_ext}
-
-# give a nice error message if people cloned the
-# repository and do not have cython installed
-if ext == '.c':
-    sources = []
-    for ext in extensions:
-        sources.extend(ext.sources)
-    if not all(os.path.isfile(s) for s in sources):
-        raise ImportError('You need `Cython` to build this project locally')
-
 
 setup(
     use_scm_version={"write_to": os.path.join("src", "eventio", "_version.py")},
-
-    ext_modules=extensions,
-    cmdclass=cmdclass,
-
-    package_data={
-        'eventio': ['*.c'],
-        'eventio.simtel': ['*.c'],
-    },
-    python_requires='>=3.8',
+    ext_modules=cythonize(extensions),
+    python_requires='>=3.9',
     install_requires=[
-        'numpy',
+        'numpy >= 1.21',
         'corsikaio ~= 0.3.3',
         'zstandard > 0.11.1', # memory leak in zstandard 0.11.1
         'setuptools_scm',