diff --git a/t/test.py b/t/test.py
index 2e730e5..4d842ad 100644
--- a/t/test.py
+++ b/t/test.py
@@ -130,7 +130,7 @@ class TestTftpy(unittest.TestCase):
             }
         factory = tftpy.TftpPacketFactory()
         for opcode in classes:
-            self.assert_(isinstance(factory.create(opcode),
+            self.assert_(isinstance(factory._TftpPacketFactory__create(opcode),
                                     classes[opcode]),
                                     "opcode %d returns the correct class" % opcode)