diff --git a/src/Group.php b/src/Group.php
index 745fccd..f52e512 100644
--- a/src/Group.php
+++ b/src/Group.php
@@ -13,9 +13,9 @@ protected function identifierError($used_identifiers) {
   }
 
   protected function validateIdentifiers($used_identifiers) {
-    $members = $this->getProp('members') ?: null;
-    $members = $members !== null ? $members->getValue() : null;
+    $members = $this->getPropValue('member') ?: null;
     $validateIdentifiers = parent::validateIdentifiers($used_identifiers);
-    return $validateIdentifiers && $members === null;
+    $validateMembers = $members === null || count($members) === 0;
+    return $validateIdentifiers && $validateMembers;
   }
 }
diff --git a/src/Members.php b/src/Members.php
index d1ca180..13607b3 100644
--- a/src/Members.php
+++ b/src/Members.php
@@ -1,5 +1,5 @@
 <?php namespace Locker\XApi;
 
 class Members extends Collection {
-  protected $member_type = 'Locker\XApi\Actor';
+  protected $member_type = 'Locker\XApi\Agent';
 }
diff --git a/tests/assets/test.json b/tests/assets/test.json
index 29ad09f..07e9051 100644
--- a/tests/assets/test.json
+++ b/tests/assets/test.json
@@ -1,11 +1,20 @@
 {
-  "actor":{
-    "mbox":"mailto:test@example.com"
-  },
-  "verb":{
-    "id":"http://adlnet.gov/expapi/verbs/voided"
-  },
-  "object":{
-    "id":"http://kiem.curatr3.com/courses/mentoropleiding"
-  }
+    "actor": {
+        "objectType": "Group",
+        "account": {
+            "homePage": "http://myaccount.bmj.com",
+            "name": "hrl"
+        },
+        "member": [
+        ]
+    },
+    "verb": {
+        "id": "http:\/\/adlnet.gov\/expapi\/verbs\/completed",
+        "display": {
+            "en-GB": "completed"
+        }
+    },
+    "object": {
+        "id": "http:\/\/localhost\/moodle\/mod\/quiz\/attempt.php?attempt=48"
+    }
 }