diff --git a/devpi_ldap/main.py b/devpi_ldap/main.py
index 825e174..75ec793 100644
--- a/devpi_ldap/main.py
+++ b/devpi_ldap/main.py
@@ -178,7 +178,7 @@ def _search(self, conn, config, **kw):
             config['base'], search_filter,
             search_scope=search_scope, attributes=[attribute_name])
         if found:
-            if any(attribute_name in x.get('attributes', {}) for x in conn.response):
+            if any(attribute_name in x.get('attributes', {}) and x['attributes'][attribute_name] for x in conn.response):
                 def extract_search(s):
                     if 'attributes' in s:
                         attributes = s['attributes'][attribute_name]