diff --git a/tests/topotests/munet/cli.py b/tests/topotests/munet/cli.py
index f58ea99d67..fc88dc320a 100644
--- a/tests/topotests/munet/cli.py
+++ b/tests/topotests/munet/cli.py
@@ -93,7 +93,7 @@ def spawn(unet, host, cmd, iow, ns_only):
             elif master_fd in r:
                 o = os.read(master_fd, 10240)
                 if o:
-                    iow.write(o.decode("utf-8"))
+                    iow.write(o.decode("utf-8", "ignore"))
                     iow.flush()
     finally:
         # restore tty settings back