diff --git a/sat/plugins/plugin_xep_0050.py b/sat/plugins/plugin_xep_0050.py
index f4cfb50c..773cde9d 100644
--- a/sat/plugins/plugin_xep_0050.py
+++ b/sat/plugins/plugin_xep_0050.py
@@ -205,7 +205,7 @@ class AdHocCommand(XMPPHandler):
 
     def _requestEb(self, failure_, request, session_id):
         if failure_.check(AdHocError):
-            error_constant = failure.value.callback_error
+            error_constant = failure_.value.callback_error
         else:
             log.error(f"unexpected error while handling request: {failure_}")
             error_constant = XEP_0050.ERROR.INTERNAL
@@ -694,7 +694,8 @@ class XEP_0050(object):
     ) -> dict:
         """Send a series of data to an ad-hoc service
 
-        @param sequence: list of
+        @param sequence: list of values to send
+            value are specified by a dict mapping var name to value.
         @param node: node of the ad-hoc commnad
         @param service_jid: jid of the ad-hoc service
             None to use profile's server