diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -1587,6 +1587,7 @@
             proc = subprocess.Popen(
                 _bytes2sys(cmd),
                 shell=True,
+                close_fds=closefds,
                 cwd=_bytes2sys(self._testtmp),
                 env=env,
             )