The 27-year-old Dutchman joined the Magpies from Ajax in the summer of 2014 but has endured an injury-plagued two years on Tyneside so far.
He has been restricted to 26 appearances – only seven of them starts – during that time, and has scored twice in all competitions. He suffered a hamstring injury in pre-season but is nearing a return to full fitness.
De Jong will link up with his brother Luuk, who had a loan spell at St. James’ Park in 2013/14, at the Philips Stadion.