Qix diagonally adjacent movement

I’m implementing a Qix clone game and I do not have any problems with implementation but rather with possible scenario.

Is this a valid scenario for this game and if yes how exactly should gameplay go in this case?

Black – Filled, Red – Current Player’s Path, Blue – Player

Step 1

If this is a possible scenario, then after completing the path player will end up with two diagonally adjacent rectangles.

Step 2

After that player can start moving from the bottom of the top rectangle to the right.

Step 3

In this case it should be immediately considered as a complete path and fill 1×1 square or player can create a path adjacent to the top of the bottom rectangle?

Step 4