The type variable `t0' is ambiguous

I'm little confused about formatting a `Text` type. I'm trying to do this:

``` haskell
import Data.Text.Format
import Data.Text.Encoding

format "{} {}" (decodeUtf8 someByteString, otherParams)
```

and this happens:

```
No instance for (Data.Text.Buildable.Buildable t0)
arising from a use of `format'
The type variable `t0' is ambiguous
Possible fix: add a type signature that fixes these type variable(s)
Note: there are several potential instances:
instance Data.Text.Buildable.Buildable Bool
-- Defined in `Data.Text.Buildable'
instance Data.Text.Buildable.Buildable
text-1.0.0.1:Data.Text.Lazy.Builder.Internal.Builder
-- Defined in `Data.Text.Buildable'
instance Data.Text.Buildable.Buildable Char
-- Defined in `Data.Text.Buildable'
...plus 32 others
```

Can you help me and explain what I'm doing wrong?