Any number of object stored as RDF array instead of plain objects

[renyuneyun]

I have a Task shaped specified in this way:

sp:Task EXTRA a {
  a [ schema:Action ];
  ...
  sp:subTask @sp:Task *
}

After serializing the data, the subtasks become RDF array, which is unexpected:

<#eb0f2eb2-e7cd-4c4a-b441-3ff507e8c621> a <https://schema.org/Action>;
    <urn:solid-planner:core#title> "eat lunch";
    <urn:solid-planner:core#subTask> _:b60404_e_b1240.
_:b60404_e_b1240 <0> <#b5836ec5-b063-4c04-9be8-0e44461e9cac>.

Am I misconfigured?

[jaxoncreed]

Could you provide the generated context and types for this data?