diff --git a/public/css/style.scss b/public/css/style.scss
index 8cf09be..0c83201 100644
--- a/public/css/style.scss
+++ b/public/css/style.scss
@@ -1,3 +1,5 @@
+@use "sass:string";
+
 @use 'theme-selector' as theme-selector;
 @use './themes/cerulean/variables' as cerulean;
 @use './themes/cosmo/variables' as cosmo;
@@ -26,7 +28,7 @@
 @use './themes/yeti/variables' as yeti;
 @use './themes/zephyr/variables' as zephyr;
 
-$theme-name: to-lower-case(theme-selector.$theme-name);
+$theme-name: string.to-lower-case(theme-selector.$theme-name);
 
 @mixin table-border-color($important: 0) {
   @if $theme-name == "cerulean" {
diff --git a/public/css/themes/zephyr/_variables.scss b/public/css/themes/zephyr/_variables.scss
index 5e8656a..ccdaef5 100644
--- a/public/css/themes/zephyr/_variables.scss
+++ b/public/css/themes/zephyr/_variables.scss
@@ -1,6 +1,8 @@
 // Zephyr 5.1.3
 // Bootswatch
 
+@use "sass:string";
+
 $theme: "zephyr" !default;
 
 //
@@ -160,4 +162,4 @@ $list-group-item-padding-x:         1.5rem !default;
 
 $breadcrumb-padding-x:              1rem !default;
 
-$breadcrumb-divider:                quote(">") !default;
+$breadcrumb-divider:                string.quote(">") !default;