diff --git a/pyzabbix/api.py b/pyzabbix/api.py
index d1daf26..5baf704 100644
--- a/pyzabbix/api.py
+++ b/pyzabbix/api.py
@@ -205,9 +205,9 @@ def _login(self, user='', password=''):
         self.auth = None
 
         if self.use_authenticate:
-            self.auth = self.user.authenticate(user=user, password=password)
+            self.auth = self.user.authenticate(username=user, password=password)
         else:
-            self.auth = self.user.login(user=user, password=password)
+            self.auth = self.user.login(username=user, password=password)
 
     def _logout(self):
         """Do logout from zabbix server."""