fixes #933 Assertion failed: [10054] in efd_unsignal
diff --git a/src/utils/efd_win.inc b/src/utils/efd_win.inc
index 3a7ea66..20e3e3f 100644
--- a/src/utils/efd_win.inc
+++ b/src/utils/efd_win.inc
@@ -263,7 +263,7 @@
         if (rc == SOCKET_ERROR && WSAGetLastError () == WSAEWOULDBLOCK)
             rc = 0;
         wsa_assert (rc != SOCKET_ERROR);
-        if (nn_fast (rc < sizeof (buf)))
+        if ((rc == SOCKET_ERROR) || (rc < sizeof (buf)))
             break;
     }
 }