diff --git a/ObservationSim/Instrument/Chip/ChipUtils.py b/ObservationSim/Instrument/Chip/ChipUtils.py
index c3bd0edc90a831ef1ea191ac182eb94a6a23f04c..be2a0546418603a57e9d863e73c4ef2909e453ae 100644
--- a/ObservationSim/Instrument/Chip/ChipUtils.py
+++ b/ObservationSim/Instrument/Chip/ChipUtils.py
@@ -196,7 +196,7 @@ def add_poisson(img, chip, exptime=150., seed=0, sky_level=0., poisson_noise=Non
     read_noise = chip.read_noise
     if dark_noise is None:
         dark_noise = chip.dark_noise
-    base_img = get_base_img(img=img, chip, read_noise=read_noise, readout_time=chip.readout_time, dark_noise=dark_noise, exptime=exptime, InputDark=None)
+    base_img = get_base_img(img=img, chip, read_noise=read_noise, readout_time=chip.readout_time, dark_noise=dark_noise, exptime=exptime, InputDark=InputDark)
     img += base_img
     img.addNoise(poisson_noise)
     # img -= read_noise**2