By default, nginx ignores invalid headers and header names containing underscores are considered invalid https://nginx.org/en/docs/http/ngx_http_core_module.html#ignore_invalid_headers https://nginx.org/en/docs/http/ngx_http_core_module.html#underscores_in_headers Changing the underscore to an hyphen would allow to keep the default nginx configuration
*** This bug has been marked as a duplicate of bug 36700 ***