diff --git a/allauth_ens/tests.py b/allauth_ens/tests.py
index b902d81..f8bf5c0 100644
--- a/allauth_ens/tests.py
+++ b/allauth_ens/tests.py
@@ -9,6 +9,7 @@ from django.core import mail
 from django.test import TestCase, override_settings
 
 from allauth.socialaccount.models import SocialAccount
+from allauth_ens.utils import get_ldap_infos
 
 import six
 from allauth_cas.test.testcases import CASTestCase
@@ -367,3 +368,11 @@ class LongTermClipperTests(CASTestCase):
         self.assertEqual(nu0, nu1)
         self.assertEqual(nsa0, nsa1)
         ldap_patcher.start()
+
+    def test_invalid_uid(self):
+        self._setup_ldap(12, "test")
+        uids = [" test", "test ", "\\test", "test)"]
+        for uid in uids:
+            with self.assertRaises(ValueError) as cm:
+                get_ldap_infos(uid)
+            self.assertIn(uid, cm.exception.message)
diff --git a/allauth_ens/utils.py b/allauth_ens/utils.py
index afd29a9..02d4c10 100644
--- a/allauth_ens/utils.py
+++ b/allauth_ens/utils.py
@@ -69,7 +69,11 @@ def extract_infos_from_ldap(infos):
 
 
 def get_ldap_infos(clipper_uid):
-    assert clipper_uid.isalnum()
+    if not clipper_uid.isalnum():
+        raise ValueError(
+            'Invalid uid "{}": contains non-alphanumeric characters'
+            .format(clipper_uid)
+        )
     data = {}
     try:
         ldap_connection = init_ldap()