--- a/setup.py	Wed Dec 29 13:33:11 2021 +0100
+++ b/setup.py	Fri Dec 31 21:24:16 2021 +0100
@@ -3,6 +3,7 @@
 
 import re
 import os
+import platform
 import sys
 try:
     from setuptools import setup
@@ -43,6 +44,58 @@
 all_requirements.extend(yaml_requirements)
 all_requirements.extend(toml_requirements)
 
+
+cmdclass = {}
+ext_modules = []
+
+#
+# Handle the optinal C-extension for Python3.7+ and CPython only.
+# PyPy does not need this.
+#
+
+if (platform.python_implementation() == "CPython"
+    and (sys.version_info[0] > 3
+         or (sys.version_info[0] == 3 and sys.version_info[1] >= 7))):
+
+    py_limited_api = False
+
+    if py_limited_api:
+        define_macros = [("Py_LIMITED_API", "0x03070000")]
+    else:
+        define_macros = []
+
+    try:
+        from setuptools import Extension
+    except ImportError:
+        from distutils.core import Extension
+
+    ext_modules = [
+        Extension(
+            name="configmix._speedups",
+            sources=["configmix/_speedups.c"],
+            define_macros=define_macros,
+            py_limited_api=py_limited_api,
+            optional=True
+        ),
+    ]
+
+    if py_limited_api:
+        #
+        # Build a wheel that is properly named using the stable API
+        #
+        try:
+            import wheel.bdist_wheel
+        except ImportError:
+            cmdclass = {}
+        else:
+            class BDistWheel(wheel.bdist_wheel.bdist_wheel):
+                def finalize_options(self):
+                    # Synchronize this with Py_LIMITED_API
+                    self.py_limited_api = 'cp37'
+                    super().finalize_options()
+
+            cmdclass = {'bdist_wheel': BDistWheel}
+
 setup(
     name="ConfigMix",
     version=version,
@@ -69,8 +122,10 @@
         "Topic :: Software Development :: Libraries :: Python Modules"
     ],
     python_requires=">=2.6",
+    ext_modules=ext_modules,
+    cmdclass=cmdclass,
     extras_require={
-        "aws" : aws_requirements,        
+        "aws" : aws_requirements,
         "toml": toml_requirements,
         "yaml": yaml_requirements,
         "all" : all_requirements,