diff --git a/src/backend/src/routers/signup.js b/src/backend/src/routers/signup.js
index f362bf067..06955a9cc 100644
--- a/src/backend/src/routers/signup.js
+++ b/src/backend/src/routers/signup.js
@@ -343,7 +343,7 @@ module.exports = eggspress(['/signup'], {
                 // uuid
                 user_uuid,
                 // email_confirm_code
-                email_confirm_code,
+                '' + email_confirm_code,
                 // email_confirm_token
                 email_confirm_token,
                 // email_confirmed