diff --git a/lib/classes/JsonApi/Schemas/BlubberComment.php b/lib/classes/JsonApi/Schemas/BlubberComment.php
index 6c0ffe347b98baf0c8c1bce81e807f7a0fc15d29..24f7e89b230aef0881d9a227ec353ddb0cf39126 100644
--- a/lib/classes/JsonApi/Schemas/BlubberComment.php
+++ b/lib/classes/JsonApi/Schemas/BlubberComment.php
@@ -62,13 +62,17 @@ class BlubberComment extends SchemaProvider
     {
         if (!$resource['external_contact']) {
             $userId = $resource['user_id'];
-            $data = $includeData ? \User::find($userId) : \User::build(['id' => $userId], false);
-            $relationships[self::REL_AUTHOR] = [
-                self::RELATIONSHIP_LINKS => [
-                    Link::RELATED => $this->createLinkToResource($data),
-                ],
-                self::RELATIONSHIP_DATA => $data,
-            ];
+            if (\User::exists($userId)) {
+                $data = $includeData ? \User::find($userId) : \User::build(['id' => $userId], false);
+                $relationships[self::REL_AUTHOR] = [
+                    self::RELATIONSHIP_DATA => $data,
+                    self::RELATIONSHIP_LINKS => [
+                        Link::RELATED => $this->createLinkToResource($data),
+                    ]
+                ];
+            } else {
+                $relationships[self::REL_AUTHOR] = [ self::RELATIONSHIP_DATA => null ];
+            }
         }
 
         return $relationships;