diff --git a/accounts/migrations/0014_auto_20180808_1436.py b/accounts/migrations/0014_auto_20180808_1436.py
new file mode 100644
index 0000000..a4f3c78
--- /dev/null
+++ b/accounts/migrations/0014_auto_20180808_1436.py
@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.13 on 2018-08-08 11:36
+from __future__ import unicode_literals
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('accounts', '0013_auto_20180625_1358'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='userattributes',
+            name='max_cpus',
+            field=models.IntegerField(default=1, help_text=b'-1 for unlimited. Any integer value', validators=[django.core.validators.MinValueValidator(-1)]),
+        ),
+        migrations.AlterField(
+            model_name='userattributes',
+            name='max_disk_size',
+            field=models.IntegerField(default=20, help_text=b'-1 for unlimited. Any integer value', validators=[django.core.validators.MinValueValidator(-1)]),
+        ),
+        migrations.AlterField(
+            model_name='userattributes',
+            name='max_instances',
+            field=models.IntegerField(default=1, help_text=b'-1 for unlimited. Any integer value', validators=[django.core.validators.MinValueValidator(-1)]),
+        ),
+        migrations.AlterField(
+            model_name='userattributes',
+            name='max_memory',
+            field=models.IntegerField(default=2048, help_text=b'-1 for unlimited. Any integer value', validators=[django.core.validators.MinValueValidator(-1)]),
+        ),
+    ]
diff --git a/accounts/migrations/0015_auto_20180808_1449.py b/accounts/migrations/0015_auto_20180808_1449.py
new file mode 100644
index 0000000..d94905a
--- /dev/null
+++ b/accounts/migrations/0015_auto_20180808_1449.py
@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.13 on 2018-08-08 11:49
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('accounts', '0014_auto_20180808_1436'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='usersshkey',
+            name='user',
+            field=models.ForeignKey(on_delete=django.db.models.deletion.DO_NOTHING, to=settings.AUTH_USER_MODEL),
+        ),
+    ]
diff --git a/accounts/models.py b/accounts/models.py
index 7ad3802..42c8051 100644
--- a/accounts/models.py
+++ b/accounts/models.py
@@ -6,8 +6,8 @@ from django.core.validators import MinValueValidator
 
 
 class UserInstance(models.Model):
-    user = models.ForeignKey(User)
-    instance = models.ForeignKey(Instance)
+    user = models.ForeignKey(User, on_delete=models.CASCADE)
+    instance = models.ForeignKey(Instance, on_delete=models.CASCADE)
     is_change = models.BooleanField(default=False)
     is_delete = models.BooleanField(default=False)
     is_vnc = models.BooleanField(default=False)
@@ -17,7 +17,7 @@ class UserInstance(models.Model):
 
 
 class UserSSHKey(models.Model):
-    user = models.ForeignKey(User)
+    user = models.ForeignKey(User, on_delete=models.DO_NOTHING)
     keyname = models.CharField(max_length=25)
     keypublic = models.CharField(max_length=500)
 
diff --git a/instances/models.py b/instances/models.py
index d91370c..b11c860 100644
--- a/instances/models.py
+++ b/instances/models.py
@@ -3,7 +3,7 @@ from computes.models import Compute
 
 
 class Instance(models.Model):
-    compute = models.ForeignKey(Compute)
+    compute = models.ForeignKey(Compute, on_delete=models.CASCADE)
     name = models.CharField(max_length=120)
     uuid = models.CharField(max_length=36)
     is_template = models.BooleanField(default=False)