diff --git a/flask/app.py b/flask/app.py
index 49c8fe10..20fa42d9 100644
--- a/flask/app.py
+++ b/flask/app.py
@@ -713,7 +713,10 @@ class Flask(_PackageBoundObject):
         return f
 
     def after_request(self, f):
-        """Register a function to be run after each request."""
+        """Register a function to be run after each request. Your function
+        must take one parameter, a :attr:`response_class` object and return
+        a new response object or the same (see :meth:`process_response`).
+        """
         self.after_request_funcs.setdefault(None, []).append(f)
         return f