diff --git a/orchestra/contrib/bills/models.py b/orchestra/contrib/bills/models.py
index c5149cc2..f14f9a33 100644
--- a/orchestra/contrib/bills/models.py
+++ b/orchestra/contrib/bills/models.py
@@ -227,7 +227,7 @@ class Bill(models.Model):
         if self.is_open:
             prefix = 'O{}'.format(prefix)
         year = timezone.now().strftime("%Y")
-        bills = cls.objects.filter(number__regex=r'^%s%s[1-9]+' % (prefix, year)
+        bills = cls.objects.filter(number__regex=r'^%s%s[1-9]+' % (prefix, year))
         last_number = bills.order_by('-number').values_list('number', flat=True).first()
         if last_number is None:
             last_number = 0
diff --git a/orchestra/contrib/plans/migrations/0002_auto_20160114_1713.py b/orchestra/contrib/plans/migrations/0002_auto_20160114_1713.py
new file mode 100644
index 00000000..f9a08d9f
--- /dev/null
+++ b/orchestra/contrib/plans/migrations/0002_auto_20160114_1713.py
@@ -0,0 +1,19 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('plans', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='rate',
+            name='plan',
+            field=models.ForeignKey(related_name='rates', to='plans.Plan', blank=True, null=True, verbose_name='plan'),
+        ),
+    ]