diff --git a/test/functional/test_framework/messages.py b/test/functional/test_framework/messages.py
index e96af7412a..945f9713ce 100755
--- a/test/functional/test_framework/messages.py
+++ b/test/functional/test_framework/messages.py
@@ -1724,8 +1724,11 @@ class msg_tx:
     __slots__ = ("tx",)
     msgtype = b"tx"
 
-    def __init__(self, tx=CTransaction()):
-        self.tx = tx
+    def __init__(self, tx=None):
+        if tx is None:
+            self.tx = CTransaction()
+        else:
+            self.tx = tx
 
     def deserialize(self, f):
         self.tx.deserialize(f)