diff --git a/tempest/services/compute/json/servers_client.py b/tempest/services/compute/json/servers_client.py
index 23c1e64..e1661c0 100644
--- a/tempest/services/compute/json/servers_client.py
+++ b/tempest/services/compute/json/servers_client.py
@@ -432,8 +432,9 @@
         return self.action(server_id, 'shelveOffload', None, **kwargs)
 
     def get_console_output(self, server_id, length):
+        kwargs = {'length': length} if length else {}
         return self.action(server_id, 'os-getConsoleOutput', 'output',
-                           common_schema.get_console_output, length=length)
+                           common_schema.get_console_output, **kwargs)
 
     def list_virtual_interfaces(self, server_id):
         """
diff --git a/tempest/services/compute/xml/servers_client.py b/tempest/services/compute/xml/servers_client.py
index 626e655..156d889 100644
--- a/tempest/services/compute/xml/servers_client.py
+++ b/tempest/services/compute/xml/servers_client.py
@@ -594,8 +594,9 @@
         return resp, body
 
     def get_console_output(self, server_id, length):
+        kwargs = {'length': length} if length else {}
         return self.action(server_id, 'os-getConsoleOutput', 'output',
-                           length=length)
+                           **kwargs)
 
     def list_virtual_interfaces(self, server_id):
         """