diff --git a/src/Dump.php b/src/Dump.php
index 24fd01b..bf96eee 100644
--- a/src/Dump.php
+++ b/src/Dump.php
@@ -34,6 +34,9 @@ class Dump {
     public function renderHtml() {
         $data = $this->getDumpContent();
 
+        $this->trace['file'] ??= "?";
+        $this->trace['line'] ??= "?";
+        
         return <<<HTML
 <pre style='-webkit-overflow-scrolling: touch;background-color: #f5f5f5;color: #4a4a4a;font-size: 12px;line-height:18px;overflow-x: auto;padding: 0.5rem 1.5rem;word-wrap: normal;white-space: pre;margin:0.33rem 0;position: relative;z-index:9000000000;'>
 <div style='color:#9f9f9f;font-size:10px;' title='{$this->trace['file']}'>[ file: {$this->trace['file']}:{$this->trace['line']} ]</div>
