Need to typeof the subkey.

lib/pool.js

@@ -236,11 +236,11 @@ function Miner(id, login, pass, ipAddress, startingDiff, messageSender, protoVer
     if (typeof(addressSplit[1]) !== 'undefined' && addressSplit[1].length === 64 && hexMatch.test(addressSplit[1])) {
         this.paymentID = addressSplit[1];
         this.payout = this.address + "." + this.paymentID;
-    } else if (addressSplit[1] !== 'undefined') {
-        this.identifier = this.identifier === 'x' ? addressSplit[1] : pass_split[0];
+    } else if (typeof(addressSplit[1]) !== 'undefined') {
+        this.identifier = pass_split[0] === 'x' ? addressSplit[1] : pass_split[0];
     }
     if (typeof(addressSplit[2]) !== 'undefined') {
-        this.identifier = this.identifier === 'x' ? addressSplit[2] : pass_split[0];
+        this.identifier = pass_split[0] === 'x' ? addressSplit[2] : pass_split[0];
     }
 
     if (pass_split.length === 2) {