diff --git a/build_ext.py b/build_ext.py
index 7a72f50..6ec955b 100644
--- a/build_ext.py
+++ b/build_ext.py
@@ -43,6 +43,9 @@ def build(setup_kwargs: Dict[Any, Any]) -> None:
                 cmdclass=dict(build_ext=BuildExt),
             )
         )
+        setup_kwargs["exclude_package_data"] = {
+            pkg: ["*.c"] for pkg in setup_kwargs["packages"]
+        }
     except Exception:
         if os.environ.get("REQUIRE_CYTHON"):
             raise