diff --git a/sbysrc/sby_core.py b/sbysrc/sby_core.py
index c56fe63f..e6802610 100644
--- a/sbysrc/sby_core.py
+++ b/sbysrc/sby_core.py
@@ -1137,9 +1137,11 @@ def instance_hierarchy_error_callback(retcode):
                 print("delete -output", file=f)
                 print("dffunmap", file=f)
                 print("stat", file=f)
-                #TODO: put -x in a conditional
-                print("write_btor -x {}-i design_{m}.info -ywmap design_btor.ywb design_{m}.btor".format("-c " if self.opt_mode == "cover" else "", m=model_name), file=f)
-                print("write_btor -s {}-i design_{m}_single.info -ywmap design_btor_single.ywb design_{m}_single.btor".format("-c " if self.opt_mode == "cover" else "", m=model_name), file=f)
+                btor_flags = ""
+                if self.opt_mode == "cover": btor_flags += "-c "
+                if self.opt_btor_aig: btor_flags += "-x "
+                print("write_btor {}-i design_{m}.info -ywmap design_btor.ywb design_{m}.btor".format(btor_flags, m=model_name), file=f)
+                print("write_btor -s {}-i design_{m}_single.info -ywmap design_btor_single.ywb design_{m}_single.btor".format(btor_flags, m=model_name), file=f)
 
             proc = SbyProc(
                 self,