diff --git a/csst_ifs_sim/csst_ifs_sim.py b/csst_ifs_sim/csst_ifs_sim.py
index ef664c6b03f987eb1a5f36dd041ccfaf7fd18137..2adbfedb0e069fd383e7f5f30c0d97ba5deeff1d 100644
--- a/csst_ifs_sim/csst_ifs_sim.py
+++ b/csst_ifs_sim/csst_ifs_sim.py
@@ -964,7 +964,7 @@ class IFSsimulator():
     :type opts: OptionParser instance
     """
 
-    def __init__(self, opts):
+    def __init__(self, configfile):
         """
         Class Constructor.
 
@@ -975,7 +975,7 @@ class IFSsimulator():
 
         ####################################
 
-        self.configfile = opts.configfile
+        self.configfile = configfile
 
         # if opts.section is None:
         #     ####self.section = 'DEFAULT'