diff --git a/stages/migrations/0021_klass_name_unique.py b/stages/migrations/0021_klass_name_unique.py
new file mode 100644
index 0000000..e636592
--- /dev/null
+++ b/stages/migrations/0021_klass_name_unique.py
@@ -0,0 +1,21 @@
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('stages', '0020_remove_old_ext_id'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='klass',
+            name='name',
+            field=models.CharField(max_length=10, unique=True, verbose_name='Nom'),
+        ),
+        migrations.AlterField(
+            model_name='student',
+            name='klass',
+            field=models.ForeignKey(blank=True, null=True, on_delete=models.deletion.PROTECT, to='stages.Klass', verbose_name='Classe'),
+        ),
+    ]
diff --git a/stages/models.py b/stages/models.py
index 79dd209..9744aca 100644
--- a/stages/models.py
+++ b/stages/models.py
@@ -45,7 +45,7 @@ class Level(models.Model):
 
 
 class Klass(models.Model):
-    name = models.CharField(max_length=10, verbose_name='Nom')
+    name = models.CharField(max_length=10, verbose_name='Nom', unique=True)
     section = models.ForeignKey(Section, verbose_name='Filière', on_delete=models.PROTECT)
     level = models.ForeignKey(Level, verbose_name='Niveau', on_delete=models.PROTECT)
     teacher = models.ForeignKey('Teacher', blank=True, null=True,
@@ -125,7 +125,7 @@ class Student(models.Model):
     instructor = models.ForeignKey('CorpContact', null=True, blank=True,
         on_delete=models.SET_NULL, verbose_name='FEE/FPP')
     klass = models.ForeignKey(Klass, verbose_name='Classe', blank=True, null=True,
-        on_delete=models.SET_NULL)
+        on_delete=models.PROTECT)
     archived = models.BooleanField(default=False, verbose_name='Archivé')
     archived_text = models.TextField(blank=True)