# M0013 no new variables (/docs/diagnostics/codes/m0013)

<Diagnostic code="M0013" />

## The mistake and the fix [#the-mistake-and-the-fix]

<div className="code-pair">

```go title="The mistake"
x := 1
x := 2
```

```go title="Fixed"
x := 1
x = 2 // [!code highlight]
```

</div>

## The fix [#the-fix]

Use = instead of :=.

See also [all error codes](/docs/diagnostics/codes) and [marmot explain](/docs/commands/explain).