diff --git a/app/assets/stylesheets/blacklight/_mixins.scss b/app/assets/stylesheets/blacklight/_mixins.scss
index c55eedf6a6..19f5b8c4f5 100644
--- a/app/assets/stylesheets/blacklight/_mixins.scss
+++ b/app/assets/stylesheets/blacklight/_mixins.scss
@@ -1,19 +1,3 @@
-// Stroke contrast
-// Ripped off from https://github.com/twbs/bootstrap/commit/c31d52499811d5c68d122db806ce27a112b489bd
-@mixin fill-yiq($color) {
-  $r: red($color);
-  $g: green($color);
-  $b: blue($color);
-
-  $yiq: (($r * 299) + ($g * 587) + ($b * 114)) / 1000;
-
-  @if ($yiq >= 150) {
-    fill: #111;
-  } @else {
-    fill: #fff;
-  }
-}
-
 // define a visually-hidden class that applies to a given breakpoint and below
 // https://getbootstrap.com/docs/5.3/helpers/visually-hidden/
 @if mixin-exists(visually-hidden) {
@@ -24,7 +8,8 @@
       }
     }
   }
-} @else if mixin-exists(sr-only) {  // Bootstrap 4 version
+} @else if mixin-exists(sr-only) {
+  // Bootstrap 4 version
   @each $infix, $breakpoint in $grid-breakpoints {
     .visually-hidden-#{$infix} {
       @include media-breakpoint-down($breakpoint) {