# E4099

A trait is used in context where a type is needed.

## Erroneous example

```{literalinclude} /sources/error_codes/4099_error/top.mbt
:language: moonbit
```

## Suggestion
If you want to refer to a trait object type, use the syntax `&Trait` instead.

```{literalinclude} /sources/error_codes/4099_fixed/top.mbt
:language: moonbit
```