PsiFile not being built for files coming from a custom VirtualFileSystem

Created my own VirtualFileSystem and FileEditorProvider. The content is coming from some database.
My implementation of VirtualFile is linked to my custom language.
The editor content is properly highlighted, nevertheless the Psi structure (PsiFile) is not being built. Does anyone have an idea why?

--.
The psi parser is properly working for files coming from LocalFileSystem.