diff --git a/mes/migrations/0004_production_assignment_device_nullable.py b/mes/migrations/0004_production_assignment_device_nullable.py
new file mode 100644
index 0000000..a2e5c67
--- /dev/null
+++ b/mes/migrations/0004_production_assignment_device_nullable.py
@@ -0,0 +1,19 @@
+# Generated by Django 5.2.8 on 2026-07-01 06:55
+
+import django.db.models.deletion
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('mes', '0003_productionassignment_production_quantity_and_more'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='productionassignment',
+            name='device',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.PROTECT, related_name='production_assignments', to='mes.device', verbose_name='设备'),
+        ),
+    ]