diff --git a/ObservationSim/Instrument/Chip/Chip.py b/ObservationSim/Instrument/Chip/Chip.py
index da6a95ec5ea20dc5c99466a09e958e77c25645b8..4fc4689581f6b065007145d96ae67690abf748d5 100755
--- a/ObservationSim/Instrument/Chip/Chip.py
+++ b/ObservationSim/Instrument/Chip/Chip.py
@@ -508,6 +508,12 @@ class Chip(FocalPlane):
                 ###     seed=SeedBiasNonuni+self.chipID,
                 ###     logger=self.logger)
                 BiasCombImg = galsim.Image(self.npix_x, self.npix_y, init_value=0) ###
+                if config["ins_effects"]["add_bias"] == True:
+                    biaslevel = self.bias_level
+                    overscan = biaslevel-2
+                elif config["ins_effects"]["add_bias"] == False:
+                    biaslevel = 0
+                    overscan = 0
 
                 # Readout noise for Biases is not generated with random seeds. So readout noise for bias images can't be reproduced.
                 if config["ins_effects"]["cosmic_ray"] == True: