diff --git a/src/Xlsx/ValueTransformer.php b/src/Xlsx/ValueTransformer.php
index 83723bf..fdf1468 100644
--- a/src/Xlsx/ValueTransformer.php
+++ b/src/Xlsx/ValueTransformer.php
@@ -87,7 +87,7 @@ public function transform($value, $type, $style)
                 return rtrim($this->sharedStrings->get($value));
             case '':
             case static::TYPE_NUMBER :
-                return Styles::FORMAT_DATE === $this->styles->get($style)
+                return $style && (Styles::FORMAT_DATE === $this->styles->get($style))
                     ? $this->dateTransformer->transform($value)
                     : $value * 1;
             default :