Problem with searchtype not working

I'm trying to use a search of user with searchtype 'equals' but all the options that I try to use give me an error:
When I try:
glpi.glpi.search_engine('user', {'criteria':[{'field':'name','searchtype':'equals','value':'xxx'}]})
I receive:
['ERROR', '; vea la documentación en su navegador en https://rejo.ll.iac.es/glpi/apirest.php/#ERROR']

Any option used in searchtype doesn't work.