Failed to create extension`uuid-ossp`

When trying to run:
```
create extension if not exists "uuid-ossp";
```

it fails with
```
error: could not open extension control file "/usr/share/postgresql/extension/uuid-ossp.control": No such file or directory
    at <anonymous> (/Users/scott/project/node_modules/pg/lib/client.js:526:17)
```

Is this meant to be supported? Or is there a specific process to get extensions working?