diff --git a/src/Issue/IssueField.php b/src/Issue/IssueField.php
index 2b498b28..aaa80110 100644
--- a/src/Issue/IssueField.php
+++ b/src/Issue/IssueField.php
@@ -355,7 +355,7 @@ public function setParentKeyOrId(string $keyOrId): static
         return $this;
     }
 
-    public function setParent(Issue $parent): void
+    public function setParent(?Issue $parent): void
     {
         $this->parent = $parent;
     }