diff --git a/lib/angulartics-segment.js b/lib/angulartics-segment.js
index ce9598a..647b227 100644
--- a/lib/angulartics-segment.js
+++ b/lib/angulartics-segment.js
@@ -62,12 +62,23 @@ angular.module('angulartics.segment', ['angulartics'])
         }
       }
     });
+    // https://segment.com/docs/libraries/analytics.js/#identify
+    // analytics.identify([userId], [traits], [options], [callback]);
+    $analyticsProvider.registerSetUsername(function (userId) {
+      try {
+        analytics.identify(userId);
+      } catch (e) {
+        if (!(e instanceof ReferenceError)) {
+          throw e;
+        }
+      }
+    });
 
     // https://segment.com/docs/libraries/analytics.js/#identify
     // analytics.identify([userId], [traits], [options], [callback]);
-    $analyticsProvider.registerSetUserProperties(function (userId, traits, options, callback) {
+    $analyticsProvider.registerSetUserProperties(function (traits, options, callback) {
       try {
-        analytics.identify(userId, traits, options, callback);
+        analytics.identify(traits, options, callback);
       } catch (e) {
         if (!(e instanceof ReferenceError)) {
           throw e;