diff --git a/Readme.md b/Readme.md
index 8f5ffd6..206108c 100644
--- a/Readme.md
+++ b/Readme.md
@@ -21,6 +21,11 @@ var obj = {};
 Emitter(obj);
 Emitter(User.prototype);
 ```
+
+  __Warning__: if you use `Emitter(Some.prototype)` on a prototype
+  you __must__ invoke `Emitter.call(this)` in the constructor to
+  clear the callbacks object, otherwise events will be shared
+  between multiple objects.
   
 ### Emitter#on(event, fn)