Update README.md

afc163 · afc163 · commit 6a8371a29d3e · 2014-06-23T11:33:06.000+08:00
diff --git a/README.md b/README.md
@@ -9,7 +9,7 @@ How to Build
 First, you should install `spm` and `spm-build`:
 
 ```
-$ npm install spm -g
+$ npm install spm@2.x -g
 $ npm install spm-build -g
 ```
 
