diff --git a/wp-includes/ms-default-filters.php b/wp-includes/ms-default-filters.php
index 47d4d4e3a..8ccbe85be 100644
--- a/wp-includes/ms-default-filters.php
+++ b/wp-includes/ms-default-filters.php
@@ -45,7 +45,7 @@ add_filter( 'wp_upload_bits', 'upload_is_file_too_big' );
 add_filter( 'import_upload_size_limit', 'fix_import_form_size' );
 add_filter( 'upload_mimes', 'check_upload_mimes' );
 add_action( 'admin_notices', 'ms_deprecated_blogs_file' );
-add_action( 'upload_size_limit', 'upload_size_limit_filter' );
+add_filter( 'upload_size_limit', 'upload_size_limit_filter' );
 
 // Mail
 add_filter( 'wp_mail_from', 'wordpressmu_wp_mail_from' );