diff --git a/extensions/mentions/src/Formatter/FormatUserMentions.php b/extensions/mentions/src/Formatter/FormatUserMentions.php
index fab597af1e..f0e6fdbb68 100644
--- a/extensions/mentions/src/Formatter/FormatUserMentions.php
+++ b/extensions/mentions/src/Formatter/FormatUserMentions.php
@@ -45,7 +45,7 @@ public function __construct(SlugManager $slugManager, TranslatorInterface $trans
     public function __invoke(Renderer $renderer, $context, string $xml)
     {
         return Utils::replaceAttributes($xml, 'USERMENTION', function ($attributes) use ($context) {
-            $user = (isset($context->getRelations()['mentionsUsers']) || $context instanceof Post)
+            $user = (($context && isset($context->getRelations()['mentionsUsers'])) || $context instanceof Post)
                 ? $context->mentionsUsers->find($attributes['id'])
                 : User::find($attributes['id']);
 
diff --git a/extensions/mentions/src/Formatter/UnparseUserMentions.php b/extensions/mentions/src/Formatter/UnparseUserMentions.php
index 4f114636a5..b150d2f7ba 100644
--- a/extensions/mentions/src/Formatter/UnparseUserMentions.php
+++ b/extensions/mentions/src/Formatter/UnparseUserMentions.php
@@ -51,7 +51,7 @@ public function __invoke($context, string $xml)
     protected function updateUserMentionTags($context, string $xml): string
     {
         return Utils::replaceAttributes($xml, 'USERMENTION', function ($attributes) use ($context) {
-            $user = (isset($context->getRelations()['mentionsUsers']) || $context instanceof Post)
+            $user = (($context && isset($context->getRelations()['mentionsUsers'])) || $context instanceof Post)
                 ? $context->mentionsUsers->find($attributes['id'])
                 : User::find($attributes['id']);