How do I use the Nightly Rust Formatter with Auto Format?

[ShiromMakkad]

My languages.toml:

[[language]]
name = "rust"
formatter = { command = "rustfmt" , args = ["+nightly"] }
auto-format = true

[language-server.rust-analyzer]
config = { cargo = { features = "all" } }

But when I write, nothing happens. I tried using log-open and searching for "rustfmt" but it didn't turn up any interesting log lines. Removing the formatter line makes the autoformat work properly, but just with the normal formatter. Are there some default args that helix uses? Or maybe helix invokes cargo to do formatting?