diff --git a/zds/mp/migrations/0008_unique_privatetopicread.py b/zds/mp/migrations/0008_unique_privatetopicread.py
new file mode 100644
index 0000000000..486219dbdd
--- /dev/null
+++ b/zds/mp/migrations/0008_unique_privatetopicread.py
@@ -0,0 +1,16 @@
+# Generated by Django 3.2.21 on 2023-11-24 22:16
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("mp", "0007_add_votes_to_private_post"),
+    ]
+
+    operations = [
+        migrations.AddConstraint(
+            model_name="privatetopicread",
+            constraint=models.UniqueConstraint(fields=("privatetopic", "user"), name="unique_privatetopicread"),
+        ),
+    ]
diff --git a/zds/mp/models.py b/zds/mp/models.py
index f1c8bbff0c..1bdcd7bbae 100644
--- a/zds/mp/models.py
+++ b/zds/mp/models.py
@@ -512,6 +512,7 @@ class PrivateTopicRead(models.Model):
     class Meta:
         verbose_name = "Message privé lu"
         verbose_name_plural = "Messages privés lus"
+        constraints = [models.UniqueConstraint(fields=["privatetopic", "user"], name="unique_privatetopicread")]
 
     privatetopic = models.ForeignKey(PrivateTopic, db_index=True, on_delete=models.CASCADE)
     privatepost = models.ForeignKey(PrivatePost, db_index=True, on_delete=models.CASCADE)