Spectrum of Kepler-444 A in the regions of interstellar absorption from the Na i D2 (top) and Na i D1 (bottom) lines. Our best fit for the intrinsic stellar spectrum (green line) yields the blue spectrum after absorption by two ISM components (absorption profiles displayed as dotted black lines, with the deeper A component blueshifted with respect to the shallower B component). Its convolution with HARPS-N instrumental profile yields the red curve, which was compared with the data over the black points. We note that the Na i D2 absorption line from the A component and the Na i D1 absorption line from the B component are blended with stellar Fe i lines, whose centers are indicated by vertical green lines.