diff --git a/packages/base-styles/CHANGELOG.md b/packages/base-styles/CHANGELOG.md
index 4074ec0ba57ff1..20d1abefde3e3d 100644
--- a/packages/base-styles/CHANGELOG.md
+++ b/packages/base-styles/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Breaking Changes
+
+-   Remove `.components-button {:focus or .is-primary}` from the `z-index()` helper ([#77621](https://github.com/WordPress/gutenberg/pull/77621)).
+
 ## 6.20.0 (2026-04-15)
 
 ## 6.19.0 (2026-04-01)
diff --git a/packages/base-styles/_z-index.scss b/packages/base-styles/_z-index.scss
index 43e45006983ff2..e04c0c25bb5b43 100644
--- a/packages/base-styles/_z-index.scss
+++ b/packages/base-styles/_z-index.scss
@@ -50,9 +50,6 @@ $z-layers: (
 	".has-child .wp-block-navigation__submenu-container": 28,
 	".has-child:hover .wp-block-navigation__submenu-container": 29,
 
-	// Active pill button
-	".components-button {:focus or .is-primary}": 1,
-
 	// The draggable element should show up above the entire UI
 	".components-draggable__clone": 1000000000,
 
diff --git a/packages/components/src/button-group/style.scss b/packages/components/src/button-group/style.scss
index d80b6961a8f113..ca0d7b1ee80337 100644
--- a/packages/components/src/button-group/style.scss
+++ b/packages/components/src/button-group/style.scss
@@ -1,6 +1,5 @@
 @use "@wordpress/base-styles/colors" as *;
 @use "@wordpress/base-styles/variables" as *;
-@use "@wordpress/base-styles/z-index" as *;
 
 .components-button-group {
 	display: inline-block;
@@ -28,7 +27,7 @@
 		&:focus,
 		&.is-primary {
 			position: relative;
-			z-index: z-index(".components-button {:focus or .is-primary}");
+			z-index: 1;
 		}
 
 		// The active button should look pressed.