diff --git a/scapy/sendrecv.py b/scapy/sendrecv.py
index 4f06c19d443..07fa4fc0062 100644
--- a/scapy/sendrecv.py
+++ b/scapy/sendrecv.py
@@ -1147,6 +1147,7 @@ def __init__(self, *args, **kwargs):
         self.thread = None  # type: Optional[Thread]
         self.results = None  # type: Optional[PacketList]
         self.exception = None  # type: Optional[Exception]
+        self.stop_cb = lambda: None  # type: Callable[[], None]
 
     def _setup_thread(self):
         # type: () -> None