r1922 self built. Windows vista

Create a new sheet, one staff, 4/4
Create a pickup measure in 1/4 by changing the actual duration
Enter 2 eights in the first measure
Enter 4 eights in the second measure
Change your mind, and drag and drop a 3/4 signature at the beginning of the score

Result : First measure become 3/4 real and actual . Other measures are still 4/4

Expected result : First measure should remain actual 1/4 and real 3/4. Other measures should be 4/4