diff --git a/runbot_merge/models/pull_requests.py b/runbot_merge/models/pull_requests.py
index 8f8ef3a7..f6dd3a47 100644
--- a/runbot_merge/models/pull_requests.py
+++ b/runbot_merge/models/pull_requests.py
@@ -852,7 +852,7 @@ class Stagings(models.Model):
         self.write({
             'active': False,
             'state': 'cancelled',
-            'reason': reason,
+            'reason': reason % args,
         })
 
     def fail(self, message, prs=None):