Jaspersoft Studio: How to make sub-report page number ascending instead of re-count the page number for each new sub-report?

My Jaspersoft Studio version: 6.5.1.final

First, as my question mentioned that the page number of each new sub-report will restart from 1. However, I want all page number can be ascending from 1 to total number of pages.

This two pictures are from single sub-report.

This one is from another single sub-report.

The above pictures show that page number is not displayed as ascending order. 

So, how to solve this problem and make them displayed as 1, 2, 3 but not 1, 2, 1?

**Note
1. The page number use the default variables $V{PAGE_NUMBER} in Jaspersoft Studio.
2. The evaluation time for variables $V{PAGE_NUMBER} is 'Now'.
3. I used an empty report only with two detail bands for insert two sub-report elements.