diff --git a/wp-admin/includes/ajax-actions.php b/wp-admin/includes/ajax-actions.php
index a4ed8efbfc..c05345e6e2 100644
--- a/wp-admin/includes/ajax-actions.php
+++ b/wp-admin/includes/ajax-actions.php
@@ -3003,7 +3003,9 @@ function wp_ajax_query_attachments() {
 		$total_posts = $count_query->found_posts;
 	}
 
-	$max_pages = ceil( $total_posts / (int) $attachments_query->query['posts_per_page'] );
+	$posts_per_page = (int) $attachments_query->query['posts_per_page'];
+
+	$max_pages = $posts_per_page ? ceil( $total_posts / $posts_per_page ) : 0;
 
 	header( 'X-WP-Total: ' . (int) $total_posts );
 	header( 'X-WP-TotalPages: ' . (int) $max_pages );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 68e1b8ecd1..fe9032465b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51484';
+$wp_version = '5.9-alpha-51485';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.