diff --git a/zds/utils/templatetags/interventions.py b/zds/utils/templatetags/interventions.py
index a7a0f0adf9..889920fc38 100644
--- a/zds/utils/templatetags/interventions.py
+++ b/zds/utils/templatetags/interventions.py
@@ -137,7 +137,7 @@ def interventions_privatetopics(user):
         '''
         select distinct t.*
         from mp_privatetopic t
-        inner join mp_privatetopic_participants p on p.privatetopic_id = t.id
+        left outer join mp_privatetopic_participants p on p.privatetopic_id = t.id
         left outer join mp_privatetopicread r on r.user_id = %s and r.privatepost_id = t.last_message_id
         where (t.author_id = %s or p.user_id = %s)
           and r.id is null
@@ -145,7 +145,8 @@ def interventions_privatetopics(user):
         [user.id, user.id, user.id])
 
     # "total" re-do the query, but there is no other way to get the length as __len__ is not available on raw queries.
-    return {'unread': privatetopics_unread, 'total': len(list(privatetopics_unread))}
+    topics = list(privatetopics_unread)
+    return {'unread': topics, 'total': len(topics)}
 
 
 @register.filter(name='alerts_list')
diff --git a/zds/utils/templatetags/tests/tests_interventions.py b/zds/utils/templatetags/tests/tests_interventions.py
new file mode 100644
index 0000000000..03a1be5005
--- /dev/null
+++ b/zds/utils/templatetags/tests/tests_interventions.py
@@ -0,0 +1,38 @@
+# coding: utf-8
+
+from django.test import TestCase
+
+from zds.member.factories import ProfileFactory
+from zds.mp.factories import PrivateTopicFactory, PrivatePostFactory
+from zds.utils.templatetags.interventions import interventions_privatetopics
+
+
+class InterventionsTest(TestCase):
+
+    def setUp(self):
+        self.author = ProfileFactory()
+        self.user = ProfileFactory()
+        self.topic = PrivateTopicFactory(author=self.author.user)
+        self.topic.participants.add(self.user.user)
+        self.post = PrivatePostFactory(
+            privatetopic=self.topic,
+            author=self.author.user,
+            position_in_topic=1)
+
+    def test_interventions_privatetopics(self):
+        result = interventions_privatetopics(self.author)
+        self.assertEqual(result['total'], 1)
+
+        result = interventions_privatetopics(self.user)
+        self.assertEqual(result['total'], 1)
+
+    def test_interventions_privatetopics_author_leave(self):
+
+        # profile1 (author) leave topic
+        move = self.topic.participants.first()
+        self.topic.author = move
+        self.topic.participants.remove(move)
+        self.topic.save()
+
+        result = interventions_privatetopics(self.user)
+        self.assertEqual(result['total'], 1)