diff --git a/tests/test_procrunner_system.py b/tests/test_procrunner_system.py
index 6e418c2..49ee78a 100644
--- a/tests/test_procrunner_system.py
+++ b/tests/test_procrunner_system.py
@@ -72,6 +72,7 @@
     ), "overridden environment variable leaked into parent process"
 
 
+@pytest.mark.xfail(sys.version_info >= (3, 9), reason="fails on 3.9.0rc1")
 def test_timeout_behaviour_legacy(tmp_path):
     start = timeit.default_timer()
     with pytest.warns(DeprecationWarning, match="timeout"):