diff --git a/purchase_request.py b/purchase_request.py
index 199e3190a9..437eaa7f00 100644
--- a/purchase_request.py
+++ b/purchase_request.py
@@ -264,6 +264,12 @@ class PurchaseRequest(ModelSQL, ModelView):
                 ])
         return [(None, '')] + [(m.model, m.name) for m in models]
 
+    @classmethod
+    def view_attributes(cls):
+        return [
+            ('/tree', 'visual', If(Eval('state') == 'cancel', 'muted', '')),
+            ]
+
     @classmethod
     def create(cls, vlist):
         for vals in vlist: