diff --git a/marietje/marietje/migrations/0006_user_blank_email.py b/marietje/marietje/migrations/0006_user_blank_email.py
new file mode 100644
index 0000000..c3e746e
--- /dev/null
+++ b/marietje/marietje/migrations/0006_user_blank_email.py
@@ -0,0 +1,18 @@
+# Generated by Django 2.0 on 2018-08-16 12:29
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('marietje', '0005_user_study'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='user',
+            name='email',
+            field=models.EmailField(blank=True, max_length=254, verbose_name='email address'),
+        ),
+    ]
diff --git a/marietje/marietje/models.py b/marietje/marietje/models.py
index 56beeea..ea34748 100644
--- a/marietje/marietje/models.py
+++ b/marietje/marietje/models.py
@@ -59,10 +59,7 @@ class User(AbstractBaseUser, PermissionsMixin):
     name = models.CharField(_('name'), max_length=30, blank=True)
     email = models.EmailField(
         _('email address'),
-        unique=True,
-        error_messages={
-            'unique': _("A user with that username already exists."),
-        },
+        blank=True,
     )
     is_staff = models.BooleanField(
         _('staff status'),