diff --git a/winsup/cygwin/fhandler_socket_unix.cc b/winsup/cygwin/fhandler_socket_unix.cc
index b0ada5d96..4dd0225f3 100644
--- a/winsup/cygwin/fhandler_socket_unix.cc
+++ b/winsup/cygwin/fhandler_socket_unix.cc
@@ -739,6 +739,9 @@ fhandler_socket_unix::grab_admin_pkt (bool peek)
   void *buffer = alloca (MAX_PATH);
   af_unix_pkt_hdr_t *packet;
 
+  if (get_unread ())
+    /* There's data in the pipe from a previous partial read of a packet. */
+    return 0;
   if (!(evt = create_event ()))
     return 0;
   if (peek)