diff --git a/test/functional/test_framework/mininode.py b/test/functional/test_framework/mininode.py
--- a/test/functional/test_framework/mininode.py
+++ b/test/functional/test_framework/mininode.py
@@ -240,7 +240,7 @@
         if not self.is_connected:
             raise IOError('Not connected')
         NetworkThread.network_event_loop.call_soon_threadsafe(
-            lambda: self._transport and self._transport.write(tmsg))
+            lambda: self._transport and not self._transport.is_closing() and self._transport.write(tmsg))
 
     # Class utility methods