diff --git a/tools/serial-io/tunslip6.c b/tools/serial-io/tunslip6.c
index 548bc1cd6..48b0ecd0f 100644
--- a/tools/serial-io/tunslip6.c
+++ b/tools/serial-io/tunslip6.c
@@ -795,9 +795,9 @@ main(int argc, char **argv)
 
     case 's':
       if(strncmp("/dev/", optarg, 5) == 0) {
-	siodev = optarg + 5;
+        siodev = optarg + 5;
       } else {
-	siodev = optarg;
+        siodev = optarg;
       }
       break;