diff --git a/conntrackt/models.py b/conntrackt/models.py
--- a/conntrackt/models.py
+++ b/conntrackt/models.py
@@ -22,7 +22,7 @@
 # Django imports.
 from django.contrib.admin.utils import NestedObjects
 from django.core.exceptions import ValidationError
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.db import models
 from django.db.models.query_utils import Q
 
@@ -248,8 +248,8 @@ class Entity(RelatedCollectorMixin, mode
 
     name = models.CharField(max_length=100)
     description = models.TextField(blank=True)
-    project = models.ForeignKey(Project)
-    location = models.ForeignKey(Location)
+    project = models.ForeignKey(Project, on_delete = models.CASCADE)
+    location = models.ForeignKey(Location, on_delete = models.CASCADE)
     objects = SearchManager()
 
     class Meta:
@@ -345,7 +345,7 @@ class Interface(RelatedCollectorMixin, m
 
     name = models.CharField(max_length=100, default='eth0')
     description = models.TextField(blank=True, default='Main network interface.')
-    entity = models.ForeignKey(Entity)
+    entity = models.ForeignKey(Entity, on_delete = models.CASCADE)
     address = models.GenericIPAddressField()
     netmask = models.GenericIPAddressField(default='255.255.255.255')
 
@@ -407,8 +407,8 @@ class Communication(RelatedCollectorMixi
         ('ICMP', 'ICMP'),
         )
 
-    source = models.ForeignKey(Interface, related_name='source_set')
-    destination = models.ForeignKey(Interface, related_name='destination_set')
+    source = models.ForeignKey(Interface, related_name='source_set', on_delete = models.CASCADE)
+    destination = models.ForeignKey(Interface, related_name='destination_set', on_delete = models.CASCADE)
     protocol = models.CharField(max_length=10, choices=PROTOCOL_CHOICES)
     port = models.IntegerField(default=0)
     description = models.TextField(blank=True)