How to update the version of Capacitor in an iOS app?

Ionic Framework
1

I need to update Capacitor in my app from version 1.0.0-beta.17 to the current 1.0.0-beta.19

I followed the instructions on this page https://capacitor.ionicframework.com/docs/ios/updating

and within my project folder entered the command:
npx cap update ios

However, when I query the version of capacitor
> npx cap --version
it returns
1.0.0-beta.17

Am I missing a step or have I misunderstood the procedure?

Thanks in advance,

David