diff --git a/src/Filter/NumberFilter.php b/src/Filter/NumberFilter.php
index a400081..1b0ebac 100644
--- a/src/Filter/NumberFilter.php
+++ b/src/Filter/NumberFilter.php
@@ -255,7 +255,7 @@ public static function numberToString($variable)
      * Units format
      * @param mixed $variable
      * @param mixed $precision
-     * @return string
+     * @return float|int|string
      */
     public static function sizeFormat(
         $variable,