diff --git a/django_etebase/migrations/0018_auto_20200624_0748.py b/django_etebase/migrations/0018_auto_20200624_0748.py
new file mode 100644
index 0000000..ec59e0c
--- /dev/null
+++ b/django_etebase/migrations/0018_auto_20200624_0748.py
@@ -0,0 +1,19 @@
+# Generated by Django 3.0.3 on 2020-06-24 07:48
+
+import django.core.validators
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_etebase', '0017_auto_20200623_0958'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='collectionitem',
+            name='uid',
+            field=models.CharField(db_index=True, max_length=43, validators=[django.core.validators.RegexValidator(message='Not a valid UID', regex='^[a-zA-Z0-9\\-_]*$')]),
+        ),
+    ]
diff --git a/django_etebase/models.py b/django_etebase/models.py
index 87b0ed1..5f7a6f2 100644
--- a/django_etebase/models.py
+++ b/django_etebase/models.py
@@ -23,7 +23,7 @@ from django.utils.crypto import get_random_string
 
 
 Base64Url256BitlValidator = RegexValidator(regex=r'^[a-zA-Z0-9\-_]{42,43}$', message='Expected a base64url.')
-UidValidator = RegexValidator(regex=r'^[a-zA-Z0-9]*$', message='Not a valid UID')
+UidValidator = RegexValidator(regex=r'^[a-zA-Z0-9\-_]*$', message='Not a valid UID')
 
 
 class Collection(models.Model):