diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 52c447d996..f20ba84d76 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -3012,8 +3012,8 @@ function wp_get_default_extension_for_mime_type( $mime_type ) {
  *
  * @since 2.0.4
  *
- * @param string   $filename File name or path.
- * @param string[] $mimes    Optional. Array of allowed mime types keyed by their file extension regex.
+ * @param string $filename File name or path.
+ * @param array  $mimes    Optional. Array of allowed mime types keyed by their file extension regex.
  *                           Defaults to the result of get_allowed_mime_types().
  * @return array {
  *     Values for the extension and mime type.
@@ -3022,7 +3022,7 @@ function wp_get_default_extension_for_mime_type( $mime_type ) {
  *     @type string|false $type File mime type, or false if the file doesn't match a mime type.
  * }
  */
-function wp_check_filetype( $filename, $mimes = null ) {
+function wp_check_filetype( $filename, $mimes = array() ) {
 	if ( empty( $mimes ) ) {
 		$mimes = get_allowed_mime_types();
 	}