diff --git a/message_subscribe.module b/message_subscribe.module
index c325d50..0d92d5e 100755
--- a/message_subscribe.module
+++ b/message_subscribe.module
@@ -6,6 +6,7 @@
  */
 
 use Drupal\message\MessageInterface;
+use Drupal\message_subscribe\Subscribers\DeliveryCandidate;
 
 /**
  * Implements hook_message_subscribe_get_subscribers().
@@ -57,9 +58,11 @@ function message_subscribe_message_subscribe_get_subscribers(MessageInterface $m
 
     foreach ($result as $row) {
 
-      $uids[$row->uid] = !empty($uids[$row->uid]) ? $uids[$row->uid] : ['notifiers' => []];
+      $uids[$row->uid] = !empty($uids[$row->uid]) ? $uids[$row->uid] : new DeliveryCandidate([], [], $row->uid);
       // Register the flag name.
-      $uids[$row->uid]['flags'][] = $row->flag_id;
+      $flags = $uids[$row->uid]->getFlags();
+      $flags[] = $row->flag_id;
+      $uids[$row->uid]->setFlags(array_unique($flags));
 
       if ($range) {
         --$range;
diff --git a/src/Subscribers.php b/src/Subscribers.php
index 6d2cdb1..e5e990e 100644
--- a/src/Subscribers.php
+++ b/src/Subscribers.php
@@ -184,6 +184,7 @@ public function sendMessage(EntityInterface $entity, MessageInterface $message,
     foreach ($uids as $uid => $delivery_candidate) {
       // Array usage is deprecated, but supported until 2.0.
       if (!$delivery_candidate instanceof DeliveryCandidateInterface) {
+        trigger_error('Usage of arrays in subscriber information is deprecated and will be removed in Message Subscribe 2.0. Use a DeliveryCandidate object instead.', E_USER_DEPRECATED);
         $delivery_candidate += ['notifiers' => []];
         $delivery_candidate = new DeliveryCandidate($delivery_candidate['flags'], $delivery_candidate['notifiers'], $uid);
       }
diff --git a/tests/modules/message_subscribe_test/message_subscribe_test.module b/tests/modules/message_subscribe_test/message_subscribe_test.module
index 6513225..47d883b 100644
--- a/tests/modules/message_subscribe_test/message_subscribe_test.module
+++ b/tests/modules/message_subscribe_test/message_subscribe_test.module
@@ -30,12 +30,18 @@ function message_subscribe_test_message_subscribe_get_subscribers_alter(array &$
   \Drupal::state('message_subscribe_test')->set('alter_hook_called', TRUE);
 
   if (!\Drupal::state('message_subscribe_test')->get('disable_subscribers_alter', FALSE)) {
-    // Add non-existent user 10001. Using an array here until array support
-    // is removed in 2.0.
-    $uids[10001] = [
-      'flags' => ['bar_flag'],
-      'notifiers' => ['email'],
-    ];
+    // Add non-existent user 10001.
+    if (\Drupal::state('message_subscribe_test')->get('use_array', FALSE)) {
+      // Test to ensure array usage still works (it will throw a deprecated
+      // notice).
+      $uids[10001] = [
+        'flags' => ['bar_flag'],
+        'notifiers' => ['email'],
+      ];
+    }
+    else {
+      $uids[10001] = new DeliveryCandidate(['bar_flag'], ['email'], 10001);
+    }
 
     // Remove user 2.
     unset($uids[2]);
diff --git a/tests/src/Kernel/SubscribersTest.php b/tests/src/Kernel/SubscribersTest.php
index 012292e..6bc3534 100644
--- a/tests/src/Kernel/SubscribersTest.php
+++ b/tests/src/Kernel/SubscribersTest.php
@@ -313,10 +313,7 @@ public function testHooks() {
     $this->assertTrue(\Drupal::state('message_subscribe_test')->get('alter_hook_called'));
     $this->assertEquals([
       4 => new DeliveryCandidate(['foo_flag'], ['email'], 4),
-      10001 => [
-        'flags' => ['bar_flag'],
-        'notifiers' => ['email'],
-      ],
+      10001 => new DeliveryCandidate(['bar_flag'], ['email'], 10001),
     ], $uids);
 
     // Disable the test module from adding a fake user.
@@ -326,6 +323,12 @@ public function testHooks() {
     // called once for each subscriber, so 2 times).
     $this->messageSubscribers->sendMessage($node, $message, [], ['entity access' => FALSE]);
     $this->assertEquals(2, \Drupal::state('message_subscribe_test')->get('message_alter_hook_called', FALSE));
+
+    // Verify legacy array support. Will trigger a notice.
+    $this->setExpectedException(\PHPUnit_Framework_Error_Deprecated::class);
+    \Drupal::state('message_subscribe_test')->set('disable_subscribers_alter', FALSE);
+    \Drupal::state('message_subscribe_test')->set('use_array', TRUE);
+    $this->messageSubscribers->sendMessage($node, $message, [], ['entity access' => FALSE]);
   }
 
   /**