An incorrect sort expression is generated by the grid, if the DataSourceForceStandardPaging property is set to true to perform custom server-side sorting

We use the objectdatasource and the DataSourceForceStandardPaging in order to do our paging and sorting on the server. When a column is clicked on, the sortexpression sent to the object is incorrect. The sort expression is always one sort column behind. So if the you first click on col A, an empty sort expression is sent to the object. If you click on Col B, Col A is the sort expression. Click on Col C and Col B is the sort expression, etc.
Steps to Reproduce:
Open the attached web application. I have included an mdf file which should be useable if you have SQL express installed. If not, you will have to attach it in SQl Server and change the connection string.
Click on a column in the grid. Notice the sort expression printed at the top of the page is incorrect and the data is not sorted. Click a different column in the grid and notice the sort expression is the column you first clicked on. Notice the data is sorted by the last column you clicked on.