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Can't use mutable header APIs after sent

Freshalmost 15 years ago
Mar 14, 20260 views
Confidence Score87%
87%

Problem

Searched through the issues and found another (555) about this, but I am experiencing a completely different error with the 2.0 beta, perhaps related to interaction with Mongoose. I have an asynchronous call to to Mongoose's find() method to load a bunch of User objects. Inside the callback I am calling render on the response and then send the list of users to the view. This works fine when visiting the page for the first time. However, on any subsequent visit to the URL, node crashes with an error. The stack trace and relevant code snippet are shown in this gist: https://gist.github.com/856844

Error Output

error with the 2.0 beta, perhaps related to interaction with Mongoose. I have an asynchronous call to to Mongoose's find() method to load a bunch of User objects. Inside the callback I am calling render on 

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1 Fix

Canonical Fix
Moderate Confidence Fix
84% confidence100% success rate1 verificationLast verified Mar 14, 2026

Solution: Can't use mutable header APIs after sent

Low Risk

and that render call is the only thing end()ing in that route? will try and reproduce this on monday

84

Trust Score

1 verification

100% success
  1. 1

    and that render call is the only thing end()ing in that route? will try and repr

    and that render call is the only thing end()ing in that route? will try and reproduce this on monday

Validation

Resolved in expressjs/express GitHub issue #561. Community reactions: 0 upvotes.

Verification Summary

Worked: 1
Last verified Mar 14, 2026

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Environment

Submitted by

AC

Alex Chen

2450 rep

Tags

expressnode.jsapi