diff --git a/src/Monolog/LogtailFormatter.php b/src/Monolog/LogtailFormatter.php
index 777d520..72155bf 100644
--- a/src/Monolog/LogtailFormatter.php
+++ b/src/Monolog/LogtailFormatter.php
@@ -27,7 +27,7 @@ public function format(array $record): string {
 
     public function formatBatch(array $records): string
     {
-        $normalized = array_values($this->normalize(array_map('self::formatRecord', $records)));
+        $normalized = array_values($this->normalize(array_map(self::class . '::formatRecord', $records)));
         return $this->toJson($normalized, true);
     }