diff --git a/constance/backends/database/migrations/0002_auto__chg_field_constance_key__add_unique_constance_key.py b/constance/backends/database/migrations/0002_auto__chg_field_constance_key__add_unique_constance_key.py
new file mode 100644
index 0000000..b06a6ac
--- /dev/null
+++ b/constance/backends/database/migrations/0002_auto__chg_field_constance_key__add_unique_constance_key.py
@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+from south.db import db
+from south.v2 import SchemaMigration
+
+
+class Migration(SchemaMigration):
+
+    def forwards(self, orm):
+        # Changing field 'Constance.key'
+        db.alter_column('constance_config', 'key', self.gf('django.db.models.fields.CharField')(unique=True, max_length=255))
+        # Adding unique constraint on 'Constance', fields ['key']
+        db.create_unique('constance_config', ['key'])
+
+    def backwards(self, orm):
+        # Removing unique constraint on 'Constance', fields ['key']
+        db.delete_unique('constance_config', ['key'])
+
+        # Changing field 'Constance.key'
+        db.alter_column('constance_config', 'key', self.gf('django.db.models.fields.TextField')())
+
+    models = {
+        'database.constance': {
+            'Meta': {'object_name': 'Constance', 'db_table': "'constance_config'"},
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'key': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '255'}),
+            'value': ('picklefield.fields.PickledObjectField', [], {})
+        }
+    }
+
+    complete_apps = ['database']