diff --git a/lib/API/MP/v1/API.php b/lib/API/MP/v1/API.php
index 0774f55ff7..f5cc3d866b 100644
--- a/lib/API/MP/v1/API.php
+++ b/lib/API/MP/v1/API.php
@@ -42,7 +42,7 @@ class API {
   }
 
   function subscribeToLists($subscriber_id, array $segments_ids) {
-    $subscriber = Subscriber::findOne((int)$subscriber_id);
+    $subscriber = Subscriber::findOne($subscriber_id);
     // throw exception when subscriber does not exist
     if(!$subscriber) {
       throw new \Exception(__('This subscriber does not exist.', 'mailpoet'));
@@ -69,7 +69,8 @@ class API {
       throw new \Exception(__(sprintf('Lists with ID %s do not exist.', implode(', ', $missing_ids)), 'mailpoet'));
     }
 
-    return SubscriberSegment::subscribeToSegments($subscriber, $found_segments_ids);
+    SubscriberSegment::subscribeToSegments($subscriber, $found_segments_ids);
+    return $subscriber->withCustomFields()->withSubscriptions()->asArray();
   }
 
   function getLists() {
diff --git a/tests/unit/API/MP/APITest.php b/tests/unit/API/MP/APITest.php
index 5c35c2bef2..336c9643ab 100644
--- a/tests/unit/API/MP/APITest.php
+++ b/tests/unit/API/MP/APITest.php
@@ -113,11 +113,8 @@ class MPAPITest extends MailPoetTest {
       )
     );
     $result = API::MP(self::VERSION)->subscribeToLists($subscriber->id, array($segment->id));
-    expect($result)->true();
-    $subscriber_segment = SubscriberSegment::where('subscriber_id', $subscriber->id)
-      ->where('segment_id', $segment->id)
-      ->findOne();
-    expect($subscriber_segment)->notEmpty();
+    expect($result['id'])->equals($subscriber->id);
+    expect($result['subscriptions'][0]['id'])->equals($segment->id);
   }
 
   function testItSubscribesSubscriberToSingleList() {
@@ -131,11 +128,9 @@ class MPAPITest extends MailPoetTest {
       )
     );
     $result = API::MP(self::VERSION)->subscribeToList($subscriber->id, $segment->id);
-    expect($result)->true();
-    $subscriber_segment = SubscriberSegment::where('subscriber_id', $subscriber->id)
-      ->where('segment_id', $segment->id)
-      ->findOne();
-    expect($subscriber_segment)->notEmpty();
+    expect($result['id'])->equals($subscriber->id);
+    expect($result['subscriptions'])->notEmpty();
+    expect($result['subscriptions'][0]['id'])->equals($segment->id);
   }
 
   function testItGetsSegments() {