denoland/deno · error

{ENABLE_ENV} must be unset or set to 1

Error message

{ENABLE_ENV} must be unset or set to 1

What it means

Build-script panic in cli/build.rs from emit_startup_order_link_args(). Startup ordering (linker function reordering via an order file) is opt-in at build time with DENO_USE_STARTUP_ORDER, and the gate is strict: the variable must be either unset or exactly the string "1". Any other value aborts the whole cargo build.

Source

Thrown at cli/build.rs:447

    if path.extension().and_then(|s| s.to_str()) == Some("ts") {
      println!("cargo:rerun-if-changed={}", path.display());
    }
  }
}

#[allow(clippy::disallowed_methods, reason = "build code")]
fn emit_startup_order_link_args(out_dir: &Path) {
  const ENABLE_ENV: &str = "DENO_USE_STARTUP_ORDER";
  const ORDER_FILE_ENV: &str = "DENO_STARTUP_ORDER_FILE";

  println!("cargo:rerun-if-env-changed={ENABLE_ENV}");
  println!("cargo:rerun-if-env-changed={ORDER_FILE_ENV}");

  if env::var_os(ENABLE_ENV).is_none() {
    return;
  }
  if env::var(ENABLE_ENV).ok().as_deref() != Some("1") {
    panic!("{ENABLE_ENV} must be unset or set to 1");
  }

  let profile = env::var("PROFILE").unwrap();
  if profile != "release" {
    panic!("startup ordering is only supported by the release profile");
  }

  let target = env::var("TARGET").unwrap();
  match target.as_str() {
    "aarch64-apple-darwin"
    | "aarch64-unknown-linux-gnu"
    | "x86_64-unknown-linux-gnu" => {}
    _ => return,
  }

  let source =
    PathBuf::from(env::var_os(ORDER_FILE_ENV).unwrap_or_else(|| {
      panic!(

View on GitHub (pinned to 9ad36f7a2c)

Solutions

1. Set the variable to exactly 1: `export DENO_USE_STARTUP_ORDER=1`
2. Or leave it unset entirely if you do not want startup ordering: `unset DENO_USE_STARTUP_ORDER`
3. Check for stray whitespace/quotes: `printf '%s' "$DENO_USE_STARTUP_ORDER" | od -c` and re-export a clean value

Example fix

# before
export DENO_USE_STARTUP_ORDER=true
cargo build --release
# after
export DENO_USE_STARTUP_ORDER=1
cargo build --release

# run before cargo build
case "${DENO_USE_STARTUP_ORDER:-}" in
  ""|1) ;;
  *) echo "DENO_USE_STARTUP_ORDER must be unset or 1, got '$DENO_USE_STARTUP_ORDER'"; exit 2;;
esac

When it happens

Trigger: Running `cargo build` for the deno crate with DENO_USE_STARTUP_ORDER set to anything except unset or "1" — typical offenders are "true", "yes", "on", "1.0", or trailing whitespace from an CI env var.

Common situations: A contributor or CI pipeline copies a generic boolean env-var convention (0/1/true/false) from other DENO_* variables to the startup-order flag, or an env file exports DENO_USE_STARTUP_ORDER=true expecting it to enable PGO/BOLT-style startup ordering.

Related errors

• startup ordering is only supported by the release profile
• {ORDER_FILE_ENV} must point to an order generated from the b
• expected file "{file}" to exist
• cli/laufey_sums.lock has no pinned laufey version — populate
• cli/laufey_sums.lock pins Laufey v{pinned} but this build ex

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/f51cd0eb9a3d7ce5. Report an issue: GitHub.