diff --git a/strip.js b/strip.js
index a5b2490..2eccd27 100644
--- a/strip.js
+++ b/strip.js
@@ -1,6 +1,7 @@
 const charset2homophones = require('./lib/generator.js')
 const encrypt            = require('./lib/encrypt.js')
 const decrypt            = require('./lib/decrypt.js')
+const fs                 = require('fs')
 
 // string
 var string         = process.argv[2]