diff --git a/styles/src/nord-dark.scss b/styles/src/nord-dark.scss
index 0a8e161..011a352 100755
--- a/styles/src/nord-dark.scss
+++ b/styles/src/nord-dark.scss
@@ -96,7 +96,7 @@ $nord16: #B48EAD; // hsl(311, 20.2, 63.1)
   $canvas-inset:         scale.$dark,
   $canvas-subtle:        scale.$base-8,
 
-  $border-default:       color.change(scale.$base-6, $alpha: 0.65),
+  $border-default:       utils.flattenColor(scale.$base-9, color.change(scale.$base-6, $alpha: 0.65)),
   $border-muted:         scale.$base-7,
   $border-subtle:        scale.$base-8,
   $shadow-default:       scale.$dark,
diff --git a/styles/src/nord-light.scss b/styles/src/nord-light.scss
index 5688c84..7917150 100755
--- a/styles/src/nord-light.scss
+++ b/styles/src/nord-light.scss
@@ -101,7 +101,7 @@ $nord16: #B48EAD; // hsl(311, 20.2, 63.1)
 
   $border-default:       scale.$base-3,
   $border-muted:         lighten(scale.$base-3, 0.1),
-  $border-subtle:        color.change(scale.$dark, $alpha: 0.15),
+  $border-subtle:        utils.flattenColor(scale.$light, color.change(scale.$dark, $alpha: 0.15)),
   $shadow-default:       scale.$base-3,
 
   $neutral-emphasisPlus: scale.$base-8,
diff --git a/styles/src/primer-dark.scss b/styles/src/primer-dark.scss
index bd62bdc..158fb96 100755
--- a/styles/src/primer-dark.scss
+++ b/styles/src/primer-dark.scss
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: MIT
 
 @use "sass:color";
+@use "settings/utils" as utils;
 
 @forward "settings/color-scale" with (
 
@@ -79,7 +80,7 @@
 
   $border-default:       scale.$base-6,
   $border-muted:         scale.$base-7,
-  $border-subtle:        color.change(scale.$base-0, $alpha: 0.1),
+  $border-subtle:        utils.flattenColor(scale.$base-9, color.change(scale.$base-0, $alpha: 0.1)),
   $shadow-default:       scale.$dark,
 
   $neutral-emphasisPlus: scale.$base-4,
diff --git a/styles/src/settings/_color-vars.scss b/styles/src/settings/_color-vars.scss
index 8494253..338eeb7 100644
--- a/styles/src/settings/_color-vars.scss
+++ b/styles/src/settings/_color-vars.scss
@@ -2,6 +2,7 @@
 
 @use "sass:color";
 @use "color-scale" as scale;
+@use "utils";
 
 $fg-default:           scale.$base-9 !default;
 $fg-muted:             scale.$base-6 !default;
@@ -15,7 +16,7 @@ $canvas-subtle:        scale.$base-0 !default;
 
 $border-default:       scale.$base-2 !default;
 $border-muted:         lighten(scale.$base-2, 0.03) !default;
-$border-subtle:        color.change(scale.$dark, $alpha: 0.15) !default;
+$border-subtle:        utils.flattenColor(scale.$light, color.change(scale.$dark, $alpha: 0.15)) !default;
 $shadow-default:       scale.$base-2 !default;
 
 // neutral is used by the .split-menu-button,