diff --git a/sign/index.js b/sign/index.js
index 45781dd4..19239ce6 100644
--- a/sign/index.js
+++ b/sign/index.js
@@ -7,6 +7,12 @@ function sign (secret, payload) {
     throw new TypeError('secret & payload required')
   }
 
-  payload = typeof payload === 'string' ? payload : JSON.stringify(payload)
+  payload = typeof payload === 'string' ? payload : toNormalizedJsonString(payload)
   return 'sha1=' + crypto.createHmac('sha1', secret).update(payload).digest('hex')
 }
+
+function toNormalizedJsonString (payload) {
+  return JSON.stringify(payload).replace(/\\u[\da-f]{4}/g, s => {
+    return s.substr(0, 2) + s.substr(2).toUpperCase()
+  })
+}