diff --git a/vendor/symposion/reviews/models.py b/vendor/symposion/reviews/models.py
index 13f76258b4dc9130078bf4d06ccdce66ae34c01d..3739bd950a71070aa3828dd8242e2bce20e66512 100644
--- a/vendor/symposion/reviews/models.py
+++ b/vendor/symposion/reviews/models.py
@@ -10,7 +10,7 @@ from django.db.models import Case, When, Value
 from django.db.models import Count
 from django.db.models.signals import post_save
 
-from django.contrib.auth.models import User
+from django.contrib.auth import get_user_model
 from django.utils.translation import ugettext_lazy as _
 
 from symposion import constants
@@ -18,6 +18,8 @@ from symposion.text_parser import parse
 from symposion.proposals.models import ProposalBase
 from symposion.schedule.models import Presentation
 
+User = get_user_model()
+
 
 class Votes(object):
     ABSTAIN = "0"
@@ -51,8 +53,16 @@ class ReviewAssignment(models.Model):
         (AUTO_ASSIGNED_LATER, _("auto-assigned, later")),
     ]
 
-    proposal = models.ForeignKey(ProposalBase, verbose_name=_("Proposal"))
-    user = models.ForeignKey(User, verbose_name=_("User"))
+    proposal = models.ForeignKey(
+        ProposalBase,
+        verbose_name=_("Proposal"),
+        on_delete=models.CASCADE,
+    )
+    user = models.ForeignKey(
+        User,
+        verbose_name=_("User"),
+        on_delete=models.CASCADE,
+    )
 
     origin = models.IntegerField(choices=ORIGIN_CHOICES, verbose_name=_("Origin"))
 
@@ -91,8 +101,17 @@ class ReviewAssignment(models.Model):
 
 
 class ProposalMessage(models.Model):
-    proposal = models.ForeignKey(ProposalBase, related_name="messages", verbose_name=_("Proposal"))
-    user = models.ForeignKey(User, verbose_name=_("User"))
+    proposal = models.ForeignKey(
+        ProposalBase,
+        related_name="messages",
+        verbose_name=_("Proposal"),
+        on_delete=models.CASCADE,
+    )
+    user = models.ForeignKey(
+        User,
+        verbose_name=_("User"),
+        on_delete=models.CASCADE,
+    )
 
     message = models.TextField(verbose_name=_("Message"))
     message_html = models.TextField(blank=True)
@@ -111,8 +130,17 @@ class ProposalMessage(models.Model):
 class Review(models.Model):
     VOTES = VOTES
 
-    proposal = models.ForeignKey(ProposalBase, related_name="reviews", verbose_name=_("Proposal"))
-    user = models.ForeignKey(User, verbose_name=_("User"))
+    proposal = models.ForeignKey(
+        ProposalBase,
+        related_name="reviews",
+        verbose_name=_("Proposal"),
+        on_delete=models.CASCADE,
+    )
+    user = models.ForeignKey(
+        User,
+        verbose_name=_("User"),
+        on_delete=models.CASCADE,
+    )
 
     # No way to encode "-0" vs. "+0" into an IntegerField, and I don't feel
     # like some complicated encoding system.
@@ -208,8 +236,17 @@ class Review(models.Model):
 class LatestVote(models.Model):
     VOTES = VOTES
 
-    proposal = models.ForeignKey(ProposalBase, related_name="votes", verbose_name=_("Proposal"))
-    user = models.ForeignKey(User, verbose_name=_("User"))
+    proposal = models.ForeignKey(
+        ProposalBase,
+        related_name="votes",
+        verbose_name=_("Proposal"),
+        on_delete=models.CASCADE,
+    )
+    user = models.ForeignKey(
+        User,
+        verbose_name=_("User"),
+        on_delete=models.CASCADE,
+    )
 
     # No way to encode "-0" vs. "+0" into an IntegerField, and I don't feel
     # like some complicated encoding system.
@@ -232,7 +269,12 @@ class LatestVote(models.Model):
 
 
 class ProposalResult(models.Model):
-    proposal = models.OneToOneField(ProposalBase, related_name="result", verbose_name=_("Proposal"))
+    proposal = models.OneToOneField(
+        ProposalBase,
+        related_name="result",
+        verbose_name=_("Proposal"),
+        on_delete=models.CASCADE,
+    )
     score = models.DecimalField(max_digits=5, decimal_places=2, default=Decimal("0.00"), verbose_name=_("Score"))
     comment_count = models.PositiveIntegerField(default=0, verbose_name=_("Comment count"))
     # vote_count only counts non-abstain votes.
@@ -297,8 +339,17 @@ class ProposalResult(models.Model):
 
 
 class Comment(models.Model):
-    proposal = models.ForeignKey(ProposalBase, related_name="comments", verbose_name=_("Proposal"))
-    commenter = models.ForeignKey(User, verbose_name=_("Commenter"))
+    proposal = models.ForeignKey(
+        ProposalBase,
+        related_name="comments",
+        verbose_name=_("Proposal"),
+        on_delete=models.CASCADE,
+    )
+    commenter = models.ForeignKey(
+        User,
+        verbose_name=_("Commenter"),
+        on_delete=models.CASCADE,
+    )
     text = models.TextField(verbose_name=_("Text"))
     text_html = models.TextField(blank=True)
 
@@ -329,9 +380,19 @@ class NotificationTemplate(models.Model):
 
 class ResultNotification(models.Model):
 
-    proposal = models.ForeignKey(ProposalBase, related_name="notifications", verbose_name=_("Proposal"))
-    template = models.ForeignKey(NotificationTemplate, null=True, blank=True,
-                                 on_delete=models.SET_NULL, verbose_name=_("Template"))
+    proposal = models.ForeignKey(
+        ProposalBase,
+        related_name="notifications",
+        verbose_name=_("Proposal"),
+        on_delete=models.CASCADE,
+    )
+    template = models.ForeignKey(
+        NotificationTemplate,
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
+        verbose_name=_("Template")
+    )
     timestamp = models.DateTimeField(default=datetime.now, verbose_name=_("Timestamp"))
     to_address = models.EmailField(verbose_name=_("To address"))
     from_address = models.EmailField(verbose_name=_("From address"))