diff --git a/addons/gamification/models/challenge.py b/addons/gamification/models/challenge.py
index e7176e8cb09..b1f297abde0 100644
--- a/addons/gamification/models/challenge.py
+++ b/addons/gamification/models/challenge.py
@@ -240,6 +240,11 @@ class gamification_challenge(osv.Model):
 
         write_res = super(gamification_challenge, self).write(cr, uid, ids, vals, context=context)
 
+        if vals.get('report_message_frequency', 'never') != 'never':
+            # _recompute_challenge_users do not set users for challenges with no reports, subscribing them now
+            for challenge in self.browse(cr, uid, ids, context=context):
+                self.message_subscribe(cr, uid, [challenge.id], [user.partner_id.id for user in challenge.user_ids], context=context)
+
         if vals.get('state') == 'inprogress':
             self._recompute_challenge_users(cr, uid, ids, context=context)
             self._generate_goals_from_challenge(cr, uid, ids, context=context)