diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index e246c36de01..99263bff091 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -933,7 +933,11 @@ class PyMemDebugTests(unittest.TestCase):
             except _testcapi.error:
                 os._exit(1)
         ''')
-        assert_python_ok('-c', code, PYTHONMALLOC=self.PYTHONMALLOC)
+        assert_python_ok(
+            '-c', code,
+            PYTHONMALLOC=self.PYTHONMALLOC,
+            MALLOC_CONF="junk:false",
+        )
 
     def test_pyobject_null_is_freed(self):
         self.check_pyobject_is_freed('check_pyobject_null_is_freed')