diff --git a/wp-includes/class-wp-theme-json.php b/wp-includes/class-wp-theme-json.php
index 7f45040221..dafbfb405c 100644
--- a/wp-includes/class-wp-theme-json.php
+++ b/wp-includes/class-wp-theme-json.php
@@ -2850,8 +2850,14 @@ class WP_Theme_JSON {
 
 				// Combine selectors with style variation's selector and add to overall style variation declarations.
 				foreach ( $variation_declarations as $current_selector => $new_declarations ) {
-					// If current selector includes block classname, remove it but leave the whitespace in.
-					$shortened_selector = str_replace( $block_metadata['selector'] . ' ', ' ', $current_selector );
+					/*
+					 * Clean up any whitespace between comma separated selectors.
+					 * This prevents these spaces breaking compound selectors such as:
+					 * - `.wp-block-list:not(.wp-block-list .wp-block-list)`
+					 * - `.wp-block-image img, .wp-block-image.my-class img`
+					 */
+					$clean_current_selector = preg_replace( '/,\s+/', ',', $current_selector );
+					$shortened_selector     = str_replace( $block_metadata['selector'], '', $clean_current_selector );
 
 					// Prepend the variation selector to the current selector.
 					$split_selectors    = explode( ',', $shortened_selector );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 14d45e4f52..c86ad3ee7c 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.8-alpha-59813';
+$wp_version = '6.8-alpha-59814';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.