diff --git a/src/pipe.cpp b/src/pipe.cpp
index 20c7f69c..9d9614b7 100644
--- a/src/pipe.cpp
+++ b/src/pipe.cpp
@@ -184,7 +184,7 @@ void zmq::pipe_t::flush ()
     if (state == terminating)
         return;
 
-    if (!outpipe->flush ())
+    if (outpipe && !outpipe->flush ())
         send_activate_read (peer);
 }