diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index b730b31f..90dbaf78 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -36,6 +36,8 @@ jobs:
 
       - name: Install dependencies
         run: |
+          pip install cython
+          python setup.py build_ext --inplace
           pip install -e .[test]
 
       - name: Run Tests
diff --git a/setup.py b/setup.py
index 49d04efa..3715b9f6 100644
--- a/setup.py
+++ b/setup.py
@@ -1,10 +1,22 @@
 from __future__ import annotations
 
-from Cython.Build import cythonize
 from setuptools import Extension, setup
+from setuptools.command.build_ext import build_ext
 
-extensions = cythonize(
-    [Extension("chgnet.graph.cygraph", ["chgnet/graph/cygraph.pyx"])]
-)
 
-setup(ext_modules=extensions)
+class BuildExt(build_ext):
+    """Custom build extension."""
+
+    def finalize_options(self):
+        """Override finalize_options to ensure we don't run cythonize when making
+        a source distribution.
+        """
+        import Cython.Build
+
+        self.distribution.ext_modules = Cython.Build.cythonize(
+            [Extension("chgnet.graph.cygraph", ["chgnet/graph/cygraph.pyx"])]
+        )
+        super().finalize_options()
+
+
+setup(cmdclass={"build_ext": BuildExt})