diff --git a/expert_witnesses/models.py b/expert_witnesses/models.py
index 623f9a8..9f1974a 100644
--- a/expert_witnesses/models.py
+++ b/expert_witnesses/models.py
@@ -15,7 +15,7 @@ class AreaOfExpertise(models.Model):
 
 
 class Expert(models.Model):
-    cases = models.ManyToManyField(Case, null=True, blank=True)
+    cases = models.ManyToManyField(Case)
     expertise = models.ManyToManyField(AreaOfExpertise)
     institute = models.CharField(max_length=255, null=True, blank=True)
     name = models.CharField(max_length=255)
diff --git a/newsletters/models.py b/newsletters/models.py
index 069e6a8..5aedf67 100644
--- a/newsletters/models.py
+++ b/newsletters/models.py
@@ -1,13 +1,13 @@
 from django.db import models
 from django.contrib.auth.admin import User
-from django.utils.timezone import now
+from django.utils import timezone
 
 
 class Newsletter(models.Model):
     body = models.TextField()
     created = models.DateTimeField(auto_now_add=True)
     creator = models.ForeignKey(User)
-    publish = models.DateTimeField(default=now())
+    publish = models.DateTimeField(default=timezone.now)
     sent = models.BooleanField(default=False)
     subject = models.CharField(max_length=255)