diff --git a/docs/guide.md b/docs/guide.md
index a96517a..4a763ea 100644
--- a/docs/guide.md
+++ b/docs/guide.md
@@ -217,7 +217,7 @@ $ DEBUG=koa* node --harmony examples/simple
 
   Since JavaScript does not allow defining function names at
   runtime, you can also set a middleware's name as `._name`.
-  This useful when you don't have control of a middleware's name.
+  This is useful when you don't have control of a middleware's name.
   For example:
 
 ```js