diff --git a/csst_ifs_sim/csst_ifs_sim.py b/csst_ifs_sim/csst_ifs_sim.py
index b1628bcb295e3517bbde41ce49b41a7b224be023..a60d0d7ab1c36810b712e369a3322cf0ecd759ce 100644
--- a/csst_ifs_sim/csst_ifs_sim.py
+++ b/csst_ifs_sim/csst_ifs_sim.py
@@ -2571,13 +2571,13 @@ class IFSsimulator():
         """
 
         self.log.debug('Starting to apply non-linearity model...')
-        self.image_b = IFSinstrumentModel.CCDnonLinearityModel(
+        self.image_b = CCDnonLinearityModel(
             self.image_b.copy())
 
         self.log.info('Non-linearity effects included.')
 
         self.log.debug('Starting to apply non-linearity model...')
-        self.image_r = IFSinstrumentModel.CCDnonLinearityModel(
+        self.image_r = CCDnonLinearityModel(
             self.image_r.copy())
 
         self.log.info('Non-linearity effects included.')