diff --git a/examples/ipv6/native-border-router/tun-bridge.c b/examples/ipv6/native-border-router/tun-bridge.c
index 827f72961..711f17dec 100644
--- a/examples/ipv6/native-border-router/tun-bridge.c
+++ b/examples/ipv6/native-border-router/tun-bridge.c
@@ -228,7 +228,7 @@ tun_output(uint8_t *data, int len)
   /* fprintf(stderr, "*** Writing to tun...%d\n", len); */
   if(write(tunfd, data, len) != len) {
     err(1, "serial_to_tun: write");
-    return 1;
+    return -1;
   }
   return 0;
 }