diff --git a/lib/linux.js b/lib/linux.js
index fe16f79..799d7ac 100644
--- a/lib/linux.js
+++ b/lib/linux.js
@@ -1,7 +1,7 @@
 var execFile = require('child_process').execFile;
 
 module.exports = function (iface, callback) {
-    execFile("cat", ["/sys/class/net/", iface, "/address"], function (err, out) {
+    execFile("cat", ["/sys/class/net/" + iface + "/address"], function (err, out) {
         if (err) {
             callback(err, null);
             return;