# HTTP.jl v2.12 incorrect header check (code: -3)

**URL:** <https://discourse.julialang.org/t/http-jl-v2-12-incorrect-header-check-code-3/140189>\
**Category:** General Usage\
**Tags:** package, http\
**Created:** [October 23, 2026, 5:42pm UTC](https://discourse.julialang.org/t/http-jl-v2-12-incorrect-header-check-code-3/140189 "2026-10-23T17:42:16Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![RGonTheNoble](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rgonthenoble/32/209422_2.png) [@RGonTheNoble](https://discourse.julialang.org/u/RGonTheNoble)\
**Post date:** [October 23, 2026, 5:42pm UTC](https://discourse.julialang.org/t/http-jl-v2-12-incorrect-header-check-code-3/140189/1 "2026-10-23T17:42:16Z")

</div>

I’m trying to migrate from v1.11 to v2.12 to call an [Inmation rest API](https://docs.inmation.com/api/1.112/webapi/index.html). It worked for v1.11 but not v2.12, and the error stacktrace I received is shown below.

```julia-auto
ERROR: CodecZlib.ZlibError("incorrect header check (code: -3)")
Stacktrace:
  [1] changemode!(stream::TranscodingStreams.TranscodingStream{CodecZlib.ZlibDecompressor, HTTP._BodyIO{…}}, newmode::Symbol)
    @ TranscodingStreams C:\Users\usr\.julia\packages\TranscodingStreams\O3BYF\src\stream.jl:794
  [2] callprocess(stream::TranscodingStreams.TranscodingStream{…}, inbuf::TranscodingStreams.Buffer, outbuf::TranscodingStreams.Buffer)
    @ TranscodingStreams C:\Users\usr\.julia\packages\TranscodingStreams\O3BYF\src\stream.jl:707
  [3] fillbuffer(stream::TranscodingStreams.TranscodingStream{CodecZlib.ZlibDecompressor, HTTP._BodyIO{…}}; eager::Bool)
    @ TranscodingStreams C:\Users\usr\.julia\packages\TranscodingStreams\O3BYF\src\stream.jl:624
  [4] fillbuffer
    @ C:\Users\usr\.julia\packages\TranscodingStreams\O3BYF\src\stream.jl:610 [inlined]
  [5] sloweof(stream::TranscodingStreams.TranscodingStream{CodecZlib.ZlibDecompressor, HTTP._BodyIO{HTTP.H2Body}})
    @ TranscodingStreams C:\Users\usr\.julia\packages\TranscodingStreams\O3BYF\src\stream.jl:222
  [6] eof
    @ C:\Users\usr\.julia\packages\TranscodingStreams\O3BYF\src\stream.jl:213 [inlined]
  [7] readbytes!(stream::TranscodingStreams.TranscodingStream{…}, b::Vector{…}, nb::Int64)
    @ TranscodingStreams C:\Users\usr\.julia\packages\TranscodingStreams\O3BYF\src\stream.jl:401
  [8] _read_all_response_bytes(io::TranscodingStreams.TranscodingStream{…}, limit::Int64)
    @ HTTP C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:1391
  [9] #_consume_incoming_response!##0
    @ C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:1817 [inlined]
 [10] _with_response_reader(f::HTTP.var"#_consume_incoming_response!##0#_consume_incoming_response!##1"{…}, incoming::HTTP._IncomingResponse{…}, decompress::Nothing)
    @ HTTP C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:1755
 [11] _consume_incoming_response!(incoming::HTTP._IncomingResponse{…}, sink::Nothing, decompress::Nothing, max_decompressed_size::Int64)
    @ HTTP C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:1815
 [12] request(method::String, url::String, h::Vector{…}, b::String; headers::Vector{…}, body::String, basicauth::Nothing, retry::Bool, retries::Int64, retry_non_idempotent::Bool, retry_if::Nothing, respect_retry_after::Bool, retry_bucket::Bool, status_exception::Bool, redirect::Bool, redirect_limit::Nothing, redirect_method::Nothing, forwardheaders::Bool, proxy::HTTP._UseTransportProxy, cookies::Bool, cookiejar::Nothing, query::Nothing, response_stream::Nothing, decompress::Nothing, max_decompressed_size::Int64, sse_callback::Nothing, max_sse_line_bytes::Int64, max_sse_event_bytes::Int64, client::Nothing, context::Nothing, connect_timeout::Nothing, request_timeout::Int64, response_header_timeout::Int64, read_idle_timeout::Int64, write_idle_timeout::Int64, expect_continue_timeout::Nothing, readtimeout::Nothing, copyheaders::Bool, pool::Nothing, canonicalize_headers::Nothing, detect_content_type::Nothing, observelayers::Nothing, retry_delays::Nothing, retry_check::Nothing, sslconfig::Nothing, socket_type_tls::Nothing, logerrors::Nothing, logtag::Nothing, trace::Nothing, verbose::Nothing, require_ssl_verification::Bool, protocol::Symbol)
    @ HTTP C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:2302
 [13] request
    @ C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:2130 [inlined]
 [14] #post#155
    @ C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:2551 [inlined]
 [15] post(::String, ::Vector{Pair{String, String}}, ::String)
    @ HTTP C:\Users\usr\.julia\packages\HTTP\Iguyh\src\http_client.jl:2549

```

I used fairly generic headers:

```julia-auto
headers = [
    "Content-Type" => "application/json",
    "Accept" => "application/json",
    "username" => credentials.username,
    "password" => credentials.password,
]

```

Is there something I’m doing wrong here, or is it just that there are incompatibilities between HTTP.jl v2.x and the HTTP/1.1 protocol that Inmation uses? I can’t make heads or tails of this error message or why it’s appearing.

---

<div class="post-metadata">

**Author:** ![quinnj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/quinnj/32/11_2.png) [@quinnj](https://discourse.julialang.org/u/quinnj)\
**Post date:** [October 23, 2026, 6:31pm UTC](https://discourse.julialang.org/t/http-jl-v2-12-incorrect-header-check-code-3/140189/2 "2026-10-23T18:31:58Z")

</div>

Thanks for the report — this is an HTTP.jl bug. HTTP.jl 2.x advertises `Accept-Encoding: gzip, deflate` (1.x only asked for gzip), and your server answers with “deflate” data in the raw form .NET’s `DeflateStream` produces, which 2.x’s decoder didn’t accept. Fixed in [Decode raw DEFLATE bodies sent as Content-Encoding: deflate - Pull Request #1511 - JuliaWeb/HTTP.jl - GitHub](https://github.com/JuliaWeb/HTTP.jl/pull/1511). Until it’s released, adding `"Accept-Encoding" => "gzip"` to your headers should get you back to the 1.11 behavior.