ets:lookup bad argument while mini_s3:list_buckets(Con)

[barcoyou]

mini_s3:manual_start().
ok
Con = mini_s3:new("X74I08TFRTOHO8GHC5QM", "IGKhLvhdSXAkt2PrIEBNUc358b-1Kk0IRTQArA==", "s3://172.16.1.178:18888").
{config,"s3://172.16.1.178:18888","X74I08TFRTOHO8GHC5QM",
"IGKhLvhdSXAkt2PrIEBNUc358b-1Kk0IRTQArA==",virtual_hosted}
mini_s3:list_buckets(Con).
** exception error: bad argument
in function ets:lookup/2
called as ets:lookup(ibrowse_lb,{"172.16.1.178",18888})
in call from ibrowse:send_req/6 (src/ibrowse.erl, line 314)
in call from mini_s3:s3_request/8 (src/mini_s3.erl, line 852)
in call from mini_s3:s3_xml_request/8 (src/mini_s3.erl, line 790)
in call from mini_s3:list_buckets/1 (src/mini_s3.erl, line 264)