Publish 2D tutorial to IOS problem

When I try to "build and run" the "2D Gameplay Tutorial Project" to MacOS it works fine. But when I try to "build and run the "2D Gameplay Tutorial Project" to IOS it fails with the following error: Assets/Scripts/2D/Spaceship/Spaceship.js(83,9): BCE0005: Unknown identifier: 'thrust'.

This is a code snippet from the Spaceship.js file where the thrust variable is initialised.

**thrust = (thrust > 0.0) ? positionalMovement.positiveAcceleration : positionalMovement.negativeAcceleration;*

Does anyone have any idea what I'm missing here?

Many thanks