Issue with page number format, when toc is relocated

That works, except that the page number sequence is as follows:

(i, ii,) iii, iv, 5, 1, 2, 3, etc ...
                  ^

where:

  - pages i and ii are suppressed in the output, as expected.
  - page iii is the preface
  - page iv is blank (double sided document)
  - page 5 is the toc
  - content follows after page 5 (numbering restarted as expected)