diff --git a/CHANGELOG b/CHANGELOG
index 8094a3b09..b24d1e986 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -78,6 +78,9 @@ NEXT (2.6)
   functions, including unittest-style Classes.  If set to False, the 
   test will not be collected.  
 
+- fix issue512: show "<notset>" for arguments which might not be set
+  in monkeypatch plugin.  Improves output in documentation.
+
 
 2.5.2
 -----------------------------------
diff --git a/_pytest/monkeypatch.py b/_pytest/monkeypatch.py
index be131bd93..9323d12f8 100644
--- a/_pytest/monkeypatch.py
+++ b/_pytest/monkeypatch.py
@@ -59,7 +59,11 @@ def derive_importpath(import_path):
 
 
 
-notset = object()
+class Notset:
+    def __repr__(self):
+        return "<notset>"
+
+notset = Notset()
 
 class monkeypatch:
     """ object keeping a record of setattr/item/env/syspath changes. """