Formula updating when rows are added on other sheet

Hello,
I want to know if it is possible for a formula to be updated when new rows are added on another sheet at the end of the rows included in the formula.

Attached example: If I add a row in Sheet1 under row 6, I want the formula in Sheet2 (cell B2) to update to

=SUM(Sheet1!A2:A7)

, but at the moment it stays as

=SUM(Sheet1!A2:A6)

Any ideas?