diff --git a/README.md b/README.md
index f69a6aef..5760501f 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@ SL(1): Cure your bad habit of mistyping
 =======================================
 
 SL (Steam Locomotive) runs across your terminal when you type "sl" as
-you meant to type "ls". It's just a joke command, and not usefull at
+you meant to type "ls". It's just a joke command, and not useful at
 all.
 
 Copyright 1993,1998,2014 Toyoda Masashi (mtoyoda@acm.org)