diff --git a/mongoengine/connection.py b/mongoengine/connection.py
index 3efb7d30..7ecc3de9 100644
--- a/mongoengine/connection.py
+++ b/mongoengine/connection.py
@@ -110,6 +110,8 @@ def get_connection(alias=DEFAULT_CONNECTION_NAME, reconnect=False):
         connection_class = Connection
         if 'replicaSet' in conn_settings:
             conn_settings['hosts_or_uri'] = conn_settings.pop('host', None)
+            # Discard port since it can't be used on ReplicaSetConnection
+            conn_settings.pop('port')
             connection_class = ReplicaSetConnection
         try:
             _connections[alias] = connection_class(**conn_settings)