diff --git a/src/os_unix.c b/src/os_unix.c
index 095e3a7..a82256c 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -5922,6 +5922,8 @@
     channel_T	*channel;
 
     open_pty(&pty_master_fd, &pty_slave_fd, &job->jv_tty_out, &job->jv_tty_in);
+    if (pty_master_fd < 0 || pty_slave_fd < 0)
+	return FAIL;
     close(pty_slave_fd);
 
     channel = add_channel();