diff --git a/MANIFEST.in b/MANIFEST.in
deleted file mode 100644
index bbd0532..0000000
--- a/MANIFEST.in
+++ /dev/null
@@ -1,5 +0,0 @@
-include README.md CHANGELOG.md LICENSE.txt MANIFEST.in setup.py requirements.txt
-recursive-include cherab *.py *.pyx *.pxd
-prune demos*
-
-
diff --git a/setup.py b/setup.py
index ae7ff58..f7a988c 100644
--- a/setup.py
+++ b/setup.py
@@ -74,6 +74,10 @@
     long_description=long_description,
     long_description_content_type="text/markdown",
     packages=find_packages(),
+    package_data={"": [
+        "**/*.pyx", "**/*.pxd",  # Needed to build Cython extensions.
+        ],
+    },
     include_package_data=True,
     install_requires=["raysect==0.8.1.*", "cherab==1.5.*"],
     ext_modules=cythonize(extensions, force=force, compiler_directives=cython_directives),