diff --git a/lib/Models/Subscriber.php b/lib/Models/Subscriber.php
index 25e8be969b..0957ee650b 100644
--- a/lib/Models/Subscriber.php
+++ b/lib/Models/Subscriber.php
@@ -491,14 +491,16 @@ class Subscriber extends Model {
       unset($data['segments']);
     }
 
-    // fields that must exist
-    $not_null_fields = array(
-      'first_name' => '',
-      'last_name' => ''
-    );
-    foreach($not_null_fields as $field => $value) {
-      if(!isset($data[$field])) {
-        $data[$field] = $value;
+    if($subscriber === false) {
+      // fields that must exist
+      $not_null_fields = array(
+        'first_name' => '',
+        'last_name' => ''
+      );
+      foreach($not_null_fields as $field => $value) {
+        if(!isset($data[$field])) {
+          $data[$field] = $value;
+        }
       }
     }