diff --git a/build_tools/build_ext.py b/build_tools/build_ext.py
index 3aa45f0241..349858ac49 100644
--- a/build_tools/build_ext.py
+++ b/build_tools/build_ext.py
@@ -57,6 +57,7 @@ def _build_cmake(self, build_dir: Path, install_dir: Path) -> None:
             build_dir,
             f"-DPython_EXECUTABLE={sys.executable}",
             f"-DPython_INCLUDE_DIR={sysconfig.get_path('include')}",
+            f"-DPython_SITEARCH={sysconfig.get_path('platlib')}",
             f"-DCMAKE_BUILD_TYPE={build_type}",
             f"-DCMAKE_INSTALL_PREFIX={install_dir}",
         ]