# XO0416: const value holds a handle

A constant is an immutable value shared by every task, not a global variable. Its type may not contain, at any depth, a `Mutex`, a channel, a task handle, or another handle type, since that would make it shared mutable state. Create the handle in `main` or a `scope` and pass it down. See core 3.1 and decision 0332.

## Example

```xo
const LOCK = Mutex.new(0)
```

## Fix

```xo
fn main(os: Os) {
  let lock = Mutex.new(0)
  lock.with(fn(var n) { n += 1 })
}
```

Run `xo explain XO0416` for this text in a terminal, or see
[section 10.6 of the specification](../../spec/core/#106-diagnostic-codes).