diff --git a/src/DocBlock/Tags/InvalidTag.php b/src/DocBlock/Tags/InvalidTag.php
index a531c03..c37ea69 100644
--- a/src/DocBlock/Tags/InvalidTag.php
+++ b/src/DocBlock/Tags/InvalidTag.php
@@ -104,6 +104,8 @@ final class InvalidTag implements Tag
         do {
             $trace = array_map(
                 static function (array $call) use ($flatten) : array {
+                    $call['args'] = $call['args'] ?? [];
+
                     array_walk_recursive($call['args'], $flatten);
 
                     return $call;