diff --git a/mailpoet/lib/Subscribers/SubscriberSaveController.php b/mailpoet/lib/Subscribers/SubscriberSaveController.php
index a6d064c824..52bf2a554b 100644
--- a/mailpoet/lib/Subscribers/SubscriberSaveController.php
+++ b/mailpoet/lib/Subscribers/SubscriberSaveController.php
@@ -304,16 +304,32 @@ class SubscriberSaveController {
 
   private function updateTags(array $data, SubscriberEntity $subscriber): void {
     $removedTags = [];
+
+    /**
+     * $data['tags'] is either an array of arrays containing name, id etc. of the tag or an array of strings - the names
+     * of the tag.
+     *
+     * Therefore we map it to be only an array of strings, containing the names of the tag.
+     */
+    $tags = array_map(
+      function($tag): string {
+        if (is_array($tag)) {
+          return array_key_exists('name', $tag) ? (string)$tag['name'] : '';
+        }
+        return (string)$tag;
+      },
+      (array)$data['tags']
+    );
     foreach ($subscriber->getSubscriberTags() as $subscriberTag) {
       $tag = $subscriberTag->getTag();
-      if (!$tag || !in_array($tag->getName(), $data['tags'], true)) {
+      if (!$tag || !in_array($tag->getName(), $tags, true)) {
         $subscriber->getSubscriberTags()->removeElement($subscriberTag);
         $removedTags[] = $subscriberTag;
       }
     }
 
     $newlyAddedTags = [];
-    foreach ($data['tags'] as $tagName) {
+    foreach ($tags as $tagName) {
       $tag = $this->tagRepository->createOrUpdate(['name' => $tagName]);
       $subscriberTag = $subscriber->getSubscriberTag($tag);
       if (!$subscriberTag) {