diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index c947ba4..f7def16 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -62,7 +62,9 @@
                 name=c_var(name), args=arglist, retval=retval).rstrip()
     if ret_type:
         ret += "\n" + mcgen(''''
-%(marshal_output_call)s
+if (!error_is_set(errp)) {
+    %(marshal_output_call)s
+}
 ''',
                             marshal_output_call=gen_marshal_output_call(name, ret_type)).rstrip()
     pop_indent(indent)