diff --git a/src/allmydata/protocol_switch.py b/src/allmydata/protocol_switch.py
index 89570436c..a17f3055c 100644
--- a/src/allmydata/protocol_switch.py
+++ b/src/allmydata/protocol_switch.py
@@ -151,6 +151,10 @@ class _FoolscapOrHttps(Protocol, metaclass=_PretendToBeNegotiation):
             30, self.transport.abortConnection
         )
 
+    def connectionLost(self, reason):
+        if self._timeout.active():
+            self._timeout.cancel()
+
     def dataReceived(self, data: bytes) -> None:
         """Handle incoming data.