diff --git a/README b/README
index 1591d66c..c034a7c5 100644
--- a/README
+++ b/README
@@ -905,7 +905,7 @@ will give output like:
  0 crw-rw---- 1 root dialout 188, 0 2012-09-11 13:49 /dev/ttyUSB0
 This means your account must have the group 'dialout' or root priviledges
 To permanently give your account the 'dialout' group:
- sudo usermod -G dialout `whoami`
+ sudo usermod -G dialout -a `whoami`
 Then logout and back in again