diff --git a/extensions/mentions/src/Formatter/UnparsePostMentions.php b/extensions/mentions/src/Formatter/UnparsePostMentions.php
index 78a692bfd5..e7866deab4 100644
--- a/extensions/mentions/src/Formatter/UnparsePostMentions.php
+++ b/extensions/mentions/src/Formatter/UnparsePostMentions.php
@@ -34,6 +34,10 @@ public function __construct(TranslatorInterface $translator)
      */
     public function __invoke($context, $xml)
     {
+        if ($xml === null) {
+            return $xml;
+        }
+
         $xml = $this->updatePostMentionTags($context, $xml);
         $xml = $this->unparsePostMentionTags($xml);
 
diff --git a/extensions/mentions/src/Formatter/UnparseTagMentions.php b/extensions/mentions/src/Formatter/UnparseTagMentions.php
index a0075cb310..c4d98debaf 100644
--- a/extensions/mentions/src/Formatter/UnparseTagMentions.php
+++ b/extensions/mentions/src/Formatter/UnparseTagMentions.php
@@ -24,6 +24,10 @@ class UnparseTagMentions
      */
     public function __invoke($context, $xml)
     {
+        if ($xml === null) {
+            return $xml;
+        }
+
         $xml = $this->updateTagMentionTags($context, $xml);
         $xml = $this->unparseTagMentionTags($xml);
 
diff --git a/extensions/mentions/src/Formatter/UnparseUserMentions.php b/extensions/mentions/src/Formatter/UnparseUserMentions.php
index 6ca5bb3dfd..cdba49b76a 100644
--- a/extensions/mentions/src/Formatter/UnparseUserMentions.php
+++ b/extensions/mentions/src/Formatter/UnparseUserMentions.php
@@ -35,6 +35,10 @@ public function __construct(TranslatorInterface $translator)
      */
     public function __invoke($context, $xml)
     {
+        if ($xml === null) {
+            return $xml;
+        }
+
         $xml = $this->updateUserMentionTags($context, $xml);
         $xml = $this->unparseUserMentionTags($xml);