REST get issues for project_id N only returns issues in subprojects of N

[grante]

I have a bunch of top-level projects, each with a handful of subprojects.

There are issues in both the top-level projects and the subprojects.

When I request issues for a top-level project using rest/issues?project_id=N I get
only issues from subprojects of N. None of the issues returned have the project
field containing id N. There _are_ top-level issues with the project field containing id N,
and I can fetch them by issue ID, but not by requesting issues with project_id=N.

How do you get issues for a top level project id?

MantisBT Version 2.25.2
Schema Version 211

[grante]

Never mind. I forgot about the default page size of 50, and the first 50 issues were all in subprojects.