diff --git a/src/_includes/base.liquid b/src/_includes/base.liquid
index 3a66d278..891ed1d7 100644
--- a/src/_includes/base.liquid
+++ b/src/_includes/base.liquid
@@ -89,7 +89,7 @@
     <script>
       (() => {
         const currentTheme = sessionStorage?.getItem('theme');
-        if (!currentTheme) sessionStorage?.setItem('theme', (this.prefersDarkScheme ? 'dark' : 'light'))
+        if (!currentTheme) sessionStorage?.setItem('theme', (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'))
         if (currentTheme === 'dark') {
           document.body.classList.add('theme__dark')
         } else if (currentTheme === 'light') {