diff --git a/ietf/doc/models.py b/ietf/doc/models.py
index 33f2ffef0..c0ba3e4d8 100644
--- a/ietf/doc/models.py
+++ b/ietf/doc/models.py
@@ -53,7 +53,7 @@ class DocumentInfo(models.Model):
     title = models.CharField(max_length=255)
 
     states = models.ManyToManyField(State, blank=True) # plain state (Active/Expired/...), IESG state, stream state
-    tags = models.ManyToManyField(DocTagName, blank=True, null=True) # Revised ID Needed, ExternalParty, AD Followup, ...
+    tags = models.ManyToManyField(DocTagName, blank=True) # Revised ID Needed, ExternalParty, AD Followup, ...
     stream = models.ForeignKey(StreamName, blank=True, null=True) # IETF, IAB, IRTF, Independent Submission
     group = models.ForeignKey(Group, blank=True, null=True) # WG, RG, IAB, IESG, Edu, Tools
 
diff --git a/ietf/doc/templatetags/ietf_filters.py b/ietf/doc/templatetags/ietf_filters.py
index db88b4d3c..50ffb8a08 100644
--- a/ietf/doc/templatetags/ietf_filters.py
+++ b/ietf/doc/templatetags/ietf_filters.py
@@ -13,7 +13,7 @@ from ietf.doc.models import ConsensusDocEvent
 from ietf.doc.utils import get_document_content
 from django import template
 from django.conf import settings
-from django.utils.html import escape, fix_ampersands
+from django.utils.html import escape
 from django.template.defaultfilters import truncatewords_html, linebreaksbr, stringfilter, striptags, urlize
 from django.template import resolve_variable
 from django.utils.safestring import mark_safe, SafeData
@@ -69,7 +69,7 @@ def parse_email_list(value):
             (name, email) = parseaddr(addr)
             if not(name):
                 name = email
-            ret.append('<a href="mailto:%s">%s</a>' % ( fix_ampersands(email), escape(name) ))
+            ret.append('<a href="mailto:%s">%s</a>' % ( email.replace('&', '&amp;'), escape(name) ))
         return mark_safe(", ".join(ret))
     else:
         return value
diff --git a/ietf/liaisons/models.py b/ietf/liaisons/models.py
index 9abfe83f0..df9357423 100644
--- a/ietf/liaisons/models.py
+++ b/ietf/liaisons/models.py
@@ -40,7 +40,7 @@ class LiaisonStatement(models.Model):
     other_identifiers = models.TextField(blank=True, null=True) # Identifiers from other bodies
     body = models.TextField(blank=True)
 
-    tags = models.ManyToManyField(LiaisonStatementTagName, blank=True, null=True)
+    tags = models.ManyToManyField(LiaisonStatementTagName, blank=True)
     attachments = models.ManyToManyField(Document, through='LiaisonStatementAttachment', blank=True)
     state = models.ForeignKey(LiaisonStatementState, default='pending')
 
@@ -212,7 +212,7 @@ class RelatedLiaisonStatement(models.Model):
 
 
 class LiaisonStatementGroupContacts(models.Model):
-    group = models.ForeignKey(Group, unique=True)
+    group = models.OneToOneField(Group)
     contacts = models.CharField(max_length=255,blank=True)
     cc_contacts = models.CharField(max_length=255,blank=True)
 
diff --git a/ietf/mailtrigger/models.py b/ietf/mailtrigger/models.py
index 20343c148..526b5f5dd 100644
--- a/ietf/mailtrigger/models.py
+++ b/ietf/mailtrigger/models.py
@@ -22,8 +22,8 @@ def clean_duplicates(addrlist):
 class MailTrigger(models.Model):
     slug = models.CharField(max_length=32, primary_key=True)
     desc = models.TextField(blank=True)
-    to   = models.ManyToManyField('Recipient', null=True, blank=True, related_name='used_in_to')
-    cc   = models.ManyToManyField('Recipient', null=True, blank=True, related_name='used_in_cc')
+    to   = models.ManyToManyField('Recipient', blank=True, related_name='used_in_to')
+    cc   = models.ManyToManyField('Recipient', blank=True, related_name='used_in_cc')
 
     class Meta:
         ordering = ["slug"]
diff --git a/ietf/meeting/models.py b/ietf/meeting/models.py
index 6df3235ab..3f000f803 100644
--- a/ietf/meeting/models.py
+++ b/ietf/meeting/models.py
@@ -416,7 +416,7 @@ class TimeSlot(models.Model):
     duration = TimedeltaField()
     location = models.ForeignKey(Room, blank=True, null=True)
     show_location = models.BooleanField(default=True, help_text="Show location in agenda.")
-    sessions = models.ManyToManyField('Session', related_name='slots', through='SchedTimeSessAssignment', null=True, blank=True, help_text=u"Scheduled session, if any.")
+    sessions = models.ManyToManyField('Session', related_name='slots', through='SchedTimeSessAssignment', blank=True, help_text=u"Scheduled session, if any.")
     modified = models.DateTimeField(auto_now=True)
     #
 
diff --git a/ietf/nomcom/models.py b/ietf/nomcom/models.py
index 8e1afc691..724f0662b 100644
--- a/ietf/nomcom/models.py
+++ b/ietf/nomcom/models.py
@@ -1,4 +1,4 @@
-# -*- coding: utf-8 -*-
+# -*- coding: utf-8 -*-
 import os
 
 from django.db import models
@@ -205,8 +205,8 @@ class Position(models.Model):
 class Feedback(models.Model):
     nomcom = models.ForeignKey('NomCom')
     author = models.EmailField(verbose_name='Author', blank=True)
-    positions = models.ManyToManyField('Position', blank=True, null=True)
-    nominees = models.ManyToManyField('Nominee', blank=True, null=True)
+    positions = models.ManyToManyField('Position', blank=True)
+    nominees = models.ManyToManyField('Nominee', blank=True)
     subject = models.TextField(verbose_name='Subject', blank=True)
     comments = EncryptedTextField(verbose_name='Comments')
     type = models.ForeignKey(FeedbackTypeName, blank=True, null=True)
diff --git a/ietf/submit/models.py b/ietf/submit/models.py
index 9bb3fed18..6e710cc6b 100644
--- a/ietf/submit/models.py
+++ b/ietf/submit/models.py
@@ -77,7 +77,7 @@ class Submission(models.Model):
         return Document.objects.filter(name=self.name).first()
 
 class SubmissionCheck(models.Model):
-    time = models.DateTimeField(auto_now=True, default=None) # The default is to make makemigrations happy
+    time = models.DateTimeField(auto_now=True)
     submission = models.ForeignKey(Submission, related_name='checks')
     checker = models.CharField(max_length=256, blank=True)
     passed = models.NullBooleanField(default=False)