Missing unique requirement for properties

At the moment it seems that in 3.5.8.5 there is no requirement for having the property unique in the namespace of the entity so it could be possible to have multiple occurrences of:
my_prop:
type: integer
my_prop:
type: string

This will default to the YAML merging behaviour, but that is not probably what we want so if we want to have just 1 property with that name is better to state it in the spec.