diff --git a/auth.py b/auth.py
index 23d5a153c026a922e5fd0f49af331f0943408079..d5e7faa4c76c070ba5b447e331686d11c24d13e0 100644
--- a/auth.py
+++ b/auth.py
@@ -41,7 +41,8 @@ class LdapManager:
 
     def groups(self, username):
         result = []
-        for _, result_dict in self.connection.search_s(self.base, ldap.SCOPE_SUBTREE, "(memberUid={})".format(username), ["cn"]):
+        # use username.lower() since memberUid is case sensitive here
+        for _, result_dict in self.connection.search_s(self.base, ldap.SCOPE_SUBTREE, "(memberUid={})".format(username.lower()), ["cn"]):
             result.append(result_dict["cn"][0])
         return result