rust-lang/cargo · error

invalid character `+` in package name: `+{toolchain}` Us

Error message

invalid character `+` in package name: `+{toolchain}`
    Use `cargo +{toolchain} update` if you meant to use the `{toolchain}` toolchain.

What it means

In `cargo update` (update.rs:74-81), each package name is checked for a leading `+`. A leading `+` is how Cargo selects a toolchain (e.g. `cargo +nightly`), so a package name starting with `+` almost always means the user misplaced the toolchain selector after `update` instead of before `cargo`.

Source

Thrown at src/bin/cargo/commands/update.rs:76

        ))
}

pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
    let mut ws = args.workspace(gctx)?;

    if args.is_present_with_zero_values("package") {
        print_available_packages(&ws)?;
    }

    let to_update = if args.contains_id("package") {
        "package"
    } else {
        "package2"
    };
    let to_update = values(args, to_update);
    for crate_name in to_update.iter() {
        if let Some(toolchain) = crate_name.strip_prefix("+") {
            return Err(anyhow!(
                "invalid character `+` in package name: `+{toolchain}`
    Use `cargo +{toolchain} update` if you meant to use the `{toolchain}` toolchain."
            )
            .into());
        }
    }

    let update_opts = UpdateOptions {
        recursive: args.flag("recursive"),
        precise: args.get_one::<String>("precise").map(String::as_str),
        to_update,
        dry_run: args.dry_run(),
        workspace: args.flag("workspace"),
        gctx,
    };

    if args.flag("breaking") {
        gctx.cli_unstable()

View on GitHub (pinned to 0e07a15537)

Solutions

1. Move the toolchain selector before the subcommand: `cargo +nightly update`.
2. If you really have a package whose name starts with `+`, that is not a valid crate name — rename it.
3. Remove the `+toolchain` token if you did not intend to override the toolchain.

Example fix

// before
$ cargo update +nightly
error: invalid character `+` in package name: `+nightly`

// after
$ cargo +nightly update

for name in &packages {
    if let Some(rest) = name.strip_prefix('+') {
        eprintln!("did you mean `cargo +{rest} update`? moving toolchain before subcommand");
        return;
    }
}

fn is_toolchain_misplacement(arg: &str) -> bool {
    arg.starts_with('+') && arg[1..].chars().all(|c| c.is_alphanumeric() || c == '-')
}

When it happens

Trigger: Running `cargo update +nightly` (toolchain after the subcommand) instead of `cargo +nightly update`. The `+nightly` is interpreted as a package name and fails this check.

Common situations: Confusing toolchain-selector argument order; scripts that append `+toolchain` to the wrong position; copying rustup examples incorrectly.

Related errors

• invalid character `+` in dependency name: `+{toolchain}`
• invalid character `+` in package name: `+{toolchain}` Us
• argument for --color must be auto, always, or never, but fou
• subcommand is required, add a subcommand to the command alia
• alias {} has unresolvable recursive definition: {} -> {}

AI-assisted analysis of rust-lang/cargo@0e07a15537 (2026-08-06). Data as JSON: /data/errors/32deb7e5dfcf6a20.json. Report an issue: GitHub.