Timeout in rpc:multicall()

[HP Wei]

I must have made some simple mistake somewhere.

I tried this:

rpc:multicall([node()], os, cmd, ["pgrep beam"]).
{["7589\n"],[]}


But, when I added Timeout = 1000,

rpc:multicall([node()], os, cmd, ["pgrep beam"], 1000).
** exited: {undef,[{rpc,multicall,[[hp@REDACTED],os,cmd,["pgrep
beam"],1000]},
                   {erl_eval,expr,3},
                   {erl_eval,exprs,4},
                   {shell,eval_loop,2}]} **

any pointer?
thanks
HP