_clear_type_cache is cpython-only
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 1e1bdbe..ab35ba4 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -425,6 +425,7 @@
             self.assertEqual(type(getattr(sys.flags, attr)), int, attr)
         self.assertTrue(repr(sys.flags))
 
+    @test.test_support.cpython_only
     def test_clear_type_cache(self):
         sys._clear_type_cache()