diff --git a/taiga/projects/history/migrations/0008_auto_20150508_1028.py b/taiga/projects/history/migrations/0008_auto_20150508_1028.py
new file mode 100644
index 00000000..bf82d6b3
--- /dev/null
+++ b/taiga/projects/history/migrations/0008_auto_20150508_1028.py
@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+import django_pgjson.fields
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('history', '0007_set_bloked_note_and_is_blocked_in_snapshots'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='historyentry',
+            name='diff',
+            field=django_pgjson.fields.JsonField(null=True, default=None, blank=True),
+            preserve_default=True,
+        ),
+        migrations.AlterField(
+            model_name='historyentry',
+            name='snapshot',
+            field=django_pgjson.fields.JsonField(null=True, default=None, blank=True),
+            preserve_default=True,
+        ),
+        migrations.AlterField(
+            model_name='historyentry',
+            name='values',
+            field=django_pgjson.fields.JsonField(null=True, default=None, blank=True),
+            preserve_default=True,
+        ),
+    ]
diff --git a/taiga/projects/history/models.py b/taiga/projects/history/models.py
index c8b38823..48b890fb 100644
--- a/taiga/projects/history/models.py
+++ b/taiga/projects/history/models.py
@@ -45,26 +45,26 @@ class HistoryEntry(models.Model):
     id = models.CharField(primary_key=True, max_length=255, unique=True,
                           editable=False, default=_generate_uuid)
 
-    user = JsonField(blank=True, default=None, null=True)
+    user = JsonField(null=True, blank=True, default=None)
     created_at = models.DateTimeField(default=timezone.now)
     type = models.SmallIntegerField(choices=HISTORY_TYPE_CHOICES)
     key = models.CharField(max_length=255, null=True, default=None, blank=True, db_index=True)
 
     # Stores the last diff
-    diff = JsonField(null=True, default=None)
+    diff = JsonField(null=True, blank=True, default=None)
 
     # Stores the last complete frozen object snapshot
-    snapshot = JsonField(null=True, default=None)
+    snapshot = JsonField(null=True, blank=True, default=None)
 
     # Stores a values of all identifiers used in
-    values = JsonField(null=True, default=None)
+    values = JsonField(null=True, blank=True, default=None)
 
     # Stores a comment
     comment = models.TextField(blank=True)
     comment_html = models.TextField(blank=True)
 
     delete_comment_date = models.DateTimeField(null=True, blank=True, default=None)
-    delete_comment_user = JsonField(blank=True, default=None, null=True)
+    delete_comment_user = JsonField(null=True, blank=True, default=None)
 
     # Flag for mark some history entries as
     # hidden. Hidden history entries are important
@@ -77,7 +77,7 @@ class HistoryEntry(models.Model):
     is_snapshot = models.BooleanField(default=False)
 
     _importing = None
-    
+
     @cached_property
     def is_change(self):
       return self.type == HistoryType.change