diff --git a/testing/test_assertrewrite.py b/testing/test_assertrewrite.py
index bedf6e27606..82c7055b968 100644
--- a/testing/test_assertrewrite.py
+++ b/testing/test_assertrewrite.py
@@ -1972,6 +1972,11 @@ def fake_mkdir(p, exist_ok=False, *, exc):
     monkeypatch.setattr(os, "makedirs", partial(fake_mkdir, exc=err))
     assert not try_makedirs(p)
 
+    err = OSError()
+    err.errno = errno.ENOSYS
+    monkeypatch.setattr(os, "makedirs", partial(fake_mkdir, exc=err))
+    assert not try_makedirs(p)
+
     # unhandled OSError should raise
     err = OSError()
     err.errno = errno.ECHILD