AppVeyor build fails

[bwasty]

I created a fresh project with the template and haven't changed any code yet, but the build on AppVeyor fails with this:

set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
rustc -V
rustc 1.34.0-nightly (b244f61b7 2019-02-12)
cargo -V
cargo 1.34.0-nightly (865cb7010 2019-02-10)
cargo test --locked
    Updating crates.io index
error: the lock file C:\projects\yage\Cargo.lock needs to be updated but --locked was passed to prevent this
Command exited with code 101

I don't understand the problem - when I run cargo update locally, nothing changes and --locked seems like 'the right thing to do' for CI.