diff --git a/wp-admin/includes/ms.php b/wp-admin/includes/ms.php
index 7796745a2e..76af47f8af 100644
--- a/wp-admin/includes/ms.php
+++ b/wp-admin/includes/ms.php
@@ -736,6 +736,9 @@ function avoid_blog_page_permalink_collision( $data, $postarr ) {
 	if ( ! is_main_site() ) {
 		return $data;
 	}
+	if ( isset( $data['post_parent'] ) && $data['post_parent'] ) {
+		return $data;
+	}
 
 	$post_name = $data['post_name'];
 	$c         = 0;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 25949db5b4..64f9af4bf2 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51854';
+$wp_version = '5.9-alpha-51855';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.