kill autocompletion is very slow on macOS

I'm on 
```
fish, version 2.7.1-1936-gf5893ba4
```

and macOS 10.14

(for some reason fish thinks its 2.7.1 but the commit its built from is ahead of fish 3)

If I type

```fish
kill |
```

And then press tab, it takes 3 full seconds before the pager shows up. I think thats way too long. Not sure whats causing this.