diff --git a/packages/@vuepress/theme-default/util/index.js b/packages/@vuepress/theme-default/util/index.js
index 0b35ccdebe..fbf641635b 100644
--- a/packages/@vuepress/theme-default/util/index.js
+++ b/packages/@vuepress/theme-default/util/index.js
@@ -1,7 +1,7 @@
 export const hashRE = /#.*$/
 export const extRE = /\.(md|html)$/
 export const endingSlashRE = /\/$/
-export const outboundRE = /^(https?:|mailto:|tel:|[a-zA-Z]{4,}:)/
+export const outboundRE = /^[a-z]+:/i
 
 export function normalize (path) {
   return decodeURI(path)