diff --git a/lib/util/index.js b/lib/util/index.js
index 01ef6ac77f..cf10c1f2dc 100644
--- a/lib/util/index.js
+++ b/lib/util/index.js
@@ -1,6 +1,6 @@
 const parseEmojis = str => {
   const emojiData = require('markdown-it-emoji/lib/data/full.json')
-  return str.replace(/:(.+?):/g, (placeholder, key) => emojiData[key] || placeholder)
+  return String(str).replace(/:(.+?):/g, (placeholder, key) => emojiData[key] || placeholder)
 }
 
 exports.normalizeHeadTag = tag => {