diff --git a/Lib/test/test_bufio.py b/Lib/test/test_bufio.py
index dc9a82dc635318..cb9cb4d0bc7e9c 100644
--- a/Lib/test/test_bufio.py
+++ b/Lib/test/test_bufio.py
@@ -28,7 +28,7 @@ def try_one(self, s):
             f.write(b"\n")
             f.write(s)
             f.close()
-            f = open(os_helper.TESTFN, "rb")
+            f = self.open(os_helper.TESTFN, "rb")
             line = f.readline()
             self.assertEqual(line, s + b"\n")
             line = f.readline()