Unable to run `cargo run --timings`

cargo run --timings worked fine initially.

But once the following code was added to ​config.nu, cargo run --timings stopped working:

source "nu_scripts/custom-completions/cargo/cargo-completions.nu"

and produced this error:

Error: nu::parser::missing_flag_param

  × Missing flag argument.
   ╭─[entry #2:1:13]
 1 │ cargo build --timings
   ·             ────┬────
   ·                 ╰── flag missing string argument
   ╰────

Start with config.nu and the sourced nu_scripts/custom-completions/cargo/cargo-completions.nu file. Reproduce the problem with cargo run --timings after adding the source line, then compare it with cargo build --timings using the reported missing flag argument. Done means cargo run --timings works with the completion script sourced.