Node REPL stdin?

sarcasm:~/src/tmp$ cat repl.js 
repl = require("repl");
repl.start("testrepl> ");
sarcasm:~/src/tmp$ node repl.js 
testrepl> 5+5
10
testrepl> sarcasm:~/src/tmp$ echo "5+5" | node repl.js 

node.js:63
    throw e;
    ^
Error: ENOTTY, Inappropriate ioctl for device
    at new Interface (readline:41:11)
    at Object.createInterface (readline:19:10)
    at new REPLServer (repl:53:27)
    at Object.start (repl:129:10)
    at Object.<anonymous> (/Users/sean/src/tmp/repl.js:2:6)
    at Module._compile (node.js:462:23)
    at Module._loadScriptSync (node.js:469:10)
    at Module.loadSync (node.js:338:12)
    at Object.runMain (node.js:522:24)
    at Array.<anonymous> (node.js:755:12)
sarcasm:~/src/tmp$