diff --git a/src/Css/Style.php b/src/Css/Style.php
index <HASH>..<HASH> 100644
--- a/src/Css/Style.php
+++ b/src/Css/Style.php
@@ -555,7 +555,7 @@ class Style
         static $cache = [];
 
         if (!isset($ref_size)) {
-            $ref_size = self::$default_font_size;
+            $ref_size = $this->__get("font_size");
         }
 
         if (!is_array($length)) {
Set default ref size to the current font size

Calculations based on font size should be calculated based on the current font size, not the default.