diff --git a/sapl/materia/forms.py b/sapl/materia/forms.py
index 054854e54..62c86451b 100644
--- a/sapl/materia/forms.py
+++ b/sapl/materia/forms.py
@@ -669,10 +669,16 @@ class AutorForm(ModelForm):
 
         autor = super(AutorForm, self).save(commit)
 
-        u = User.objects.get_or_create(
-            username=autor.username,
-            email=autor.email)
-        u = u[0]
+        try:
+            u = User.objects.get(
+                username=autor.username,
+                email=autor.email)
+        except ObjectDoesNotExist:
+            msg = _('Este nome de usuario não está cadastrado. ' +
+                    'Por favor, cadastre-o no Administrador do ' +
+                    'Sistema antes de adicioná-lo como Autor')
+            raise ValidationError(msg)
+
         u.set_password(self.cleaned_data['senha'])
         u.is_active = False
         u.save()
diff --git a/sapl/materia/migrations/0046_auto_20160825_1833.py b/sapl/materia/migrations/0046_auto_20160825_1833.py
new file mode 100644
index 000000000..25b586eb3
--- /dev/null
+++ b/sapl/materia/migrations/0046_auto_20160825_1833.py
@@ -0,0 +1,22 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.9.7 on 2016-08-25 21:33
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('materia', '0045_auto_20160823_1658'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='autor',
+            name='user',
+            field=models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL),
+        ),
+    ]
diff --git a/sapl/materia/models.py b/sapl/materia/models.py
index c38d76c0a..26380163c 100644
--- a/sapl/materia/models.py
+++ b/sapl/materia/models.py
@@ -208,7 +208,9 @@ class TipoAutor(models.Model):
 
 
 class Autor(models.Model):
-    user = models.ForeignKey(User)
+    user = models.ForeignKey(User,
+                             blank=True,
+                             null=True)
     partido = models.ForeignKey(Partido, blank=True, null=True)
     comissao = models.ForeignKey(Comissao, blank=True, null=True)
     parlamentar = models.ForeignKey(Parlamentar, blank=True, null=True)