diff --git a/taiga/projects/attachments/migrations/0004_auto_20150508_1141.py b/taiga/projects/attachments/migrations/0004_auto_20150508_1141.py
new file mode 100644
index 00000000..1e1855cf
--- /dev/null
+++ b/taiga/projects/attachments/migrations/0004_auto_20150508_1141.py
@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+from django.conf import settings
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('attachments', '0003_auto_20150114_0954'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='attachment',
+            name='owner',
+            field=models.ForeignKey(verbose_name='owner', blank=True, related_name='change_attachments', to=settings.AUTH_USER_MODEL, null=True),
+            preserve_default=True,
+        ),
+    ]
diff --git a/taiga/projects/attachments/models.py b/taiga/projects/attachments/models.py
index df466c18..c95c0f6b 100644
--- a/taiga/projects/attachments/models.py
+++ b/taiga/projects/attachments/models.py
@@ -49,7 +49,7 @@ def get_attachment_file_path(instance, filename):
 
 
 class Attachment(models.Model):
-    owner = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=False,
+    owner = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, blank=True,
                               related_name="change_attachments",
                               verbose_name=_("owner"))
     project = models.ForeignKey("projects.Project", null=False, blank=False,