diff --git a/wp-includes/block-supports/layout.php b/wp-includes/block-supports/layout.php
index 67d6a3f1b7..4da4f24b23 100644
--- a/wp-includes/block-supports/layout.php
+++ b/wp-includes/block-supports/layout.php
@@ -615,6 +615,9 @@ function wp_render_layout_support_flag( $block_content, $block ) {
 			$processor->add_class( $class_name );
 		}
 		return $processor->get_updated_html();
+	} elseif ( ! $block_supports_layout ) {
+		// Ensure layout classnames are not injected if there is no layout support.
+		return $block_content;
 	}
 
 	$global_settings = wp_get_global_settings();
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 06767d3b73..636d21b9b2 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.5-alpha-57327';
+$wp_version = '6.5-alpha-57328';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.