Rust problem with Clap value_of_lossy function

Question

I have a structure:

pub struct Config {
    files: Vec<String>,
....
}

I use Clap library to get parameters from the command line

.arg(
            Arg::with_name("files")
                .value_name("FILE")
                .help("Input file(s)")
                .multiple(true)
                .default_value("-"),
        )

when I try to assign values to struct:

Config {
        files: matches.value_of_lossy("files").unwrap(),
....

I got the following error:

error[E0308]: mismatched types
  --> src/lib.rs:42:16
   |
42 |         files: matches.value_of_lossy("files").unwrap(),
   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `Vec<String>`, found `Cow<'_, str>`
   |
   = note: expected struct `Vec<String>`
                found enum `Cow<'_, str>`

For more information about this error, try `rustc --explain E0308`.
error: could not compile `catr` (lib) due to previous error

How can I get the string Vector from Clap? I do not understand how to transform a Cow and use it.