EC
ERR_HTTP2_CONNECT_SCHEME
Node.jsERRORNotableHTTP/2HIGH confidence

HTTP/2 CONNECT request must not include :scheme pseudo-header

Production Risk

Low — only affects HTTP/2 tunnelling code.

What this means

Thrown when an HTTP/2 CONNECT request includes the :scheme pseudo-header. RFC 7540 forbids :scheme in CONNECT requests; the scheme is implicit from the tunnel target in :authority.

Why it happens
  1. 1Including :scheme in a CONNECT request
  2. 2Generic request-building code that always adds :scheme
How to reproduce

Triggered when :scheme is present in an HTTP/2 CONNECT request.

trigger — this will error
trigger — this will error
const req = client.request({
  ':method': 'CONNECT',
  ':authority': 'target.example.com:443',
  ':scheme': 'https', // forbidden
});

expected output

Error [ERR_HTTP2_CONNECT_SCHEME]: The :scheme header is forbidden for CONNECT requests

Fix

Remove :scheme from CONNECT requests

WHEN When constructing HTTP/2 CONNECT requests

Remove :scheme from CONNECT requests
const req = client.request({
  ':method': 'CONNECT',
  ':authority': 'target.example.com:443',
});

Why this works

Omitting :scheme satisfies the RFC 7540 CONNECT constraint.

Code examples
Triggerjs
const req = client.request({
  ':method': 'CONNECT',
  ':authority': 'target.example.com:443',
  ':scheme': 'https', // forbidden
});  // this triggers ERR_HTTP2_CONNECT_SCHEME
Handle in try/catchjs
try {
  // operation that may throw ERR_HTTP2_CONNECT_SCHEME
  riskyOperation()
} catch (err) {
  if (err.code === 'ERR_HTTP2_CONNECT_SCHEME') {
    console.error('ERR_HTTP2_CONNECT_SCHEME:', err.message)
  } else {
    throw err
  }
}
Defensive pattern to avoid itjs
// Validate inputs before calling the operation
function safe_err_http2_connect_scheme(...args) {
  // validate args here
  return performOperation(...args)
}
What not to do

✕ Use the same header template for CONNECT and regular requests

:scheme is forbidden in CONNECT and must be stripped.

Same error in other languages
ValueErrorin Python→
Sources
Official documentation ↗

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