Analysis of a detached eclipsing binary at near the turnoff point of the open cluster NGC 6791 in Kepler field

•We analyzed high-precision Kepler photometry and ESO Science Archieve data.•Data from the Kepler makes it clear that the system inclination is close to 90.•The secondary star is not expected to have evolved significantly.•The primary star is at near the turnoff point of the open cluster NGC 6791.