Render function with N-space - what am I doing wrong here to pass children?

[mitya33]

As far as I know this is valid use of Vue's h() function:

h(NSpace, {size: 'small'}, [
	h('span', {textContent: 'foo'}),
	h('span', {textContent: 'bar'}),
])

Yet this throws the warning:

_[Vue warn]: Non-function value encountered for default slot. Prefer function slots for better performance. _

What would be correct here? I've tried:

h(NSpace, {size: 'small'}, [
	() => h('span', {textContent: 'foo'}),
	() => h('span', {textContent: 'bar'}),
])

...but that no joy.