diff --git a/wp-includes/admin-bar.php b/wp-includes/admin-bar.php
index ba85e1f1ae..6eca9d05b6 100644
--- a/wp-includes/admin-bar.php
+++ b/wp-includes/admin-bar.php
@@ -431,6 +431,11 @@ function wp_admin_bar_customize_menu( $wp_admin_bar ) {
 		return;
 	}
 
+	// Don't show if a block theme is activated.
+	if ( wp_is_block_template_theme() ) {
+		return;
+	}
+
 	$current_url = ( is_ssl() ? 'https://' : 'http://' ) . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
 	if ( is_customize_preview() && $wp_customize->changeset_uuid() ) {
 		$current_url = remove_query_arg( 'customize_changeset_uuid', $current_url );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 11715fdffc..a7a2122b6f 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-52133';
+$wp_version = '5.9-alpha-52134';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.