diff --git a/uid-number.js b/uid-number.js
index 93f372b..1cd511c 100644
--- a/uid-number.js
+++ b/uid-number.js
@@ -33,7 +33,7 @@ function uidNumber (uid, gid, cb) {
   child_process.execFile( process.execPath
                         , [getter, uid, gid]
                         , function (code, out, err) {
-    if (er) return cb(new Error("could not get uid/gid\n" + err))
+    if (err) return cb(new Error("could not get uid/gid\n" + err))
     try {
       out = JSON.parse(out+"")
     } catch (ex) {