diff --git a/src/PhpPresentation/Shape/Chart/Axis.php b/src/PhpPresentation/Shape/Chart/Axis.php
index 86e187870..7786dca9b 100644
--- a/src/PhpPresentation/Shape/Chart/Axis.php
+++ b/src/PhpPresentation/Shape/Chart/Axis.php
@@ -42,6 +42,8 @@ class Axis implements ComparableInterface
     public const CROSSES_MIN = 'min';
     public const CROSSES_MAX = 'max';
 
+    public const DEFAULT_FORMAT_CODE = 'general';
+
     /**
      * Title.
      *
@@ -59,7 +61,7 @@ class Axis implements ComparableInterface
      *
      * @var string
      */
-    private $formatCode = '';
+    private $formatCode = self::DEFAULT_FORMAT_CODE;
 
     /**
      * Font.
@@ -543,4 +545,4 @@ public function setTickLabelPosition(string $value = self::TICK_LABEL_POSITION_N
 
         return $this;
     }
-}
+}
\ No newline at end of file