diff --git a/tempest/services/object_storage/account_client.py b/tempest/services/object_storage/account_client.py
index 4dc588f..410d0a0 100644
--- a/tempest/services/object_storage/account_client.py
+++ b/tempest/services/object_storage/account_client.py
@@ -222,7 +222,7 @@
 
         url = '?format=%s' % self.format
         if params:
-            url += '&%s' + urllib.urlencode(params)
+            url += '&%s' % urllib.urlencode(params)
 
         headers = {}
         if metadata: