diff --git a/wp-includes/class-wp-theme-json.php b/wp-includes/class-wp-theme-json.php
index bcbf16b762..15780efc34 100644
--- a/wp-includes/class-wp-theme-json.php
+++ b/wp-includes/class-wp-theme-json.php
@@ -1681,7 +1681,7 @@ class WP_Theme_JSON {
 										$spacing_rule['selector']
 									);
 								} else {
-									$format          = static::ROOT_BLOCK_SELECTOR === $selector ? '.%2$s %3$s' : '%1$s-%2$s %3$s';
+									$format          = static::ROOT_BLOCK_SELECTOR === $selector ? ':root :where(.%2$s)%3$s' : ':root :where(%1$s-%2$s)%3$s';
 									$layout_selector = sprintf(
 										$format,
 										$selector,
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 2c0e8eaf33..8acea37f6e 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6.2-alpha-58982';
+$wp_version = '6.6.2-alpha-58986';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.