"Trigger.get" with "host" param returns nothing

Sending "trigger.get" request with "host" param returns exception with non informative text:
JSON-rpc error generation failed. No such error "".

Debug log:
20: Sending: {"params": {"host": "Server", "startSearch": true, "search": {"description": "test trigger"}}, "jsonrpc": "2.0", "method": "trigger.get", "auth": "1f701fff1fasdf2bfcd2ec7b0f9114ad", "id": 1}
10: Sending headers:

{'Content-Type': 'application/json-rpc', 'User-Agent': 'python/zabbix_api'}

20: Response Code: 200
10: Response Body: {u'jsonrpc': u'2.0', u'id': 1, u'error': {u'message': u'System error.', u'code': -32400, u'data': u'JSON-rpc error generation failed. No such error "".'}}
(u'Error -32400: System error., JSON-rpc error generation failed. No such error "". while sending {"params": {"host": "Server", "startSearch": true, "search": {"description": "test trigger"}}, "jsonrpc": "2.0", "method": "trigger.get", "auth": "1f701fff1faf812bfcd2ec7b0f9114ad", "id": 1}', -32400)