We show that any pushbroom hyperspectral imager can be converted into a windowing one by only attaching in front of it a simple dispersive element. The resulting device displays the same spectral resolution than the former one. To test this idea we have built a pushbroom imaging spectrograph in our laboratory. A plane transmission grating has been used as the dispersive element. We point out the main characteristics of these devices and we show some illustrative results.