diff --git a/CHANGELOG b/CHANGELOG
index 0c8f8a4c..cad1f318 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+- Force l'unicité des logins clipper
 - Nouveau site du COF en wagtail
 - Meilleurs affichage des longues listes de spectacles à cocher dans BdA-Revente
 - Bugfix : les pages de la revente ne sont plus accessibles qu'aux membres du
diff --git a/gestioncof/migrations/0016_unique_clippers.py b/gestioncof/migrations/0016_unique_clippers.py
new file mode 100644
index 00000000..dced5148
--- /dev/null
+++ b/gestioncof/migrations/0016_unique_clippers.py
@@ -0,0 +1,45 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.18 on 2019-01-14 21:36
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+def empty_clippers_to_null(apps, schema_editor):
+    CofProfile = apps.get_model("gestioncof", "CofProfile")
+    CofProfile.objects.filter(login_clipper="").update(login_clipper=None)
+
+
+def null_clippers_to_empty(apps, schema_editor):
+    CofProfile = apps.get_model("gestioncof", "CofProfile")
+    CofProfile.objects.filter(login_clipper__isnull=True).update(login_clipper="")
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [("gestioncof", "0015_psql_choices_niveaux")]
+
+    operations = [
+        # First, only set null to True (unique is still False)
+        migrations.AlterField(
+            model_name="cofprofile",
+            name="login_clipper",
+            field=models.CharField(
+                blank=True, max_length=32, null=True, verbose_name="Login clipper"
+            ),
+        ),
+        # Then, set all empty login_clippers to null
+        migrations.RunPython(empty_clippers_to_null),
+        # Finally set unique to True
+        migrations.AlterField(
+            model_name="cofprofile",
+            name="login_clipper",
+            field=models.CharField(
+                blank=True,
+                max_length=32,
+                null=True,
+                unique=True,
+                verbose_name="Login clipper",
+            ),
+        ),
+    ]
diff --git a/gestioncof/models.py b/gestioncof/models.py
index 98b947a1..e4975fc4 100644
--- a/gestioncof/models.py
+++ b/gestioncof/models.py
@@ -46,7 +46,9 @@ class CofProfile(models.Model):
     )
 
     user = models.OneToOneField(User, on_delete=models.CASCADE, related_name="profile")
-    login_clipper = models.CharField("Login clipper", max_length=32, blank=True)
+    login_clipper = models.CharField(
+        "Login clipper", max_length=32, blank=True, unique=True, null=True
+    )
     is_cof = models.BooleanField("Membre du COF", default=False)
     phone = models.CharField("Téléphone", max_length=20, blank=True)
     occupation = models.CharField(