diff --git a/src/Monolog/Handler/RotatingFileHandler.php b/src/Monolog/Handler/RotatingFileHandler.php
index a4a5ba44..78703e45 100644
--- a/src/Monolog/Handler/RotatingFileHandler.php
+++ b/src/Monolog/Handler/RotatingFileHandler.php
@@ -50,7 +50,7 @@ class RotatingFileHandler extends StreamHandler
         $this->maxFiles = (int) $maxFiles;
         $this->nextRotation = new \DateTimeImmutable('tomorrow');
         $this->filenameFormat = '{filename}-{date}';
-        $this->dateFormat = 'Y-m-d';
+        $this->dateFormat = self::FILE_PER_DAY;
 
         parent::__construct($this->getTimedFilename(), $level, $bubble, $filePermission, $useLocking);
     }