diff --git a/themes/book/layouts/partials/docs/html-head.html b/themes/book/layouts/partials/docs/html-head.html
index ec87be2..b24730d 100644
--- a/themes/book/layouts/partials/docs/html-head.html
+++ b/themes/book/layouts/partials/docs/html-head.html
@@ -16,7 +16,7 @@
 {{ end -}}
 
 <!-- Theme stylesheet, you can customize scss by creating `assets/custom.scss` in your website -->
-{{- $styles := resources.Get "book.scss" | resources.ExecuteAsTemplate "book.scss" . | resources.ToCSS | resources.Minify | resources.Fingerprint }}
+{{- $styles := resources.Get "book.scss" | resources.ExecuteAsTemplate "book.scss" . | css.Sass | resources.Minify | resources.Fingerprint }}
 <link rel="stylesheet" href="{{ $styles.RelPermalink }}" integrity="{{ $styles.Data.Integrity }}">
 
 {{- if default true .Site.Params.BookSearch }}