[ScrollSmoother error "_mainInstance.content is not a function" with SvelteKit]

I am having the same error come up, but I am using a Remix project:

 

import { gsap } from 'gsap/dist/gsap'
import { ScrollSmoother } from 'gsap/dist/ScrollSmoother'

...

useEffect(() => {
    gsap.registerPlugin(ScrollSmoother)
    scrollSmoother.current = ScrollSmoother.create({
      smooth: 1,
      effects: true,
      content: '#smooth-content'
    })
  }, [])

I get this error:

TypeError: _mainInstance.content is not a function
    at ScrollSmoother.create (http://localhost:3000/build/_shared/chunk-2KGHTWMG.js:4566:55)
    at http://localhost:3000/build/routes/($role)-V6X7IM6L.js:5769:67
    at commitHookEffectListMount (http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:16436:34)
    at invokePassiveEffectMountInDEV (http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:17845:19)
    at invokeEffectsInDev (http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:19194:19)
    at commitDoubleInvokeEffectsInDEV (http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:19179:15)
    at flushPassiveEffectsImpl (http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:18996:13)
    at flushPassiveEffects (http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:18940:22)
    at http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:18821:17
    at workLoop (http://localhost:3000/build/_shared/chunk-VKRUHKJ5.js:195:42)

Any insights?