diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 788933816..bcb1adee8 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -2019,7 +2019,7 @@ function wp_mkdir_p( $target ) {
 	$target = str_replace( '//', '/', $target );
 
 	// safe mode fails with a trailing slash under certain PHP versions.
-	$target = untrailingslashit($target);
+	$target = rtrim($target, '/'); // Use rtrim() instead of untrailingslashit to avoid formatting.php dependency.
 	if ( empty($target) )
 		$target = '/';