No Fit Puzzle - how can this be??

This is an interesting all hardwood puzzle from our shop in an attractive format. It was designed by famous Dutch puzzle designer Niek Neuwahl in the 1990's.

You are given a puzzle base with 5 pcs forming a square.  The objective is to fit an additional small square pc into the puzzle and still make a square!  Doesn't look possible; but, of course it is.

Please CLick Here to View a Video on this Puzzle

Very clever.  Please view the video for details, including the solution (if you want to know...)