diff --git a/base/univention-system-setup/umc/python/setup/util.py b/base/univention-system-setup/umc/python/setup/util.py
index a79c7c0d61..3db77618e5 100644
--- a/base/univention-system-setup/umc/python/setup/util.py
+++ b/base/univention-system-setup/umc/python/setup/util.py
@@ -917,6 +917,8 @@ def is_ldap_base(ldap_base):
        >>> is_ldap_base('cn=foo,c=ZZ,dc=foo,dc=bar')
        False
        """
+       if not ldap.dn.is_dn(ldap_base):
+               return False
        match = is_ldap_base.RE.match(ldap_base)
        return match is not None and not any(part.upper().startswith('C=') and not part.upper()[2:] in is_ldap_base.CC for part in ldap.dn.explode_dn(ldap_base))