diff --git a/sbysrc/sby_core.py b/sbysrc/sby_core.py
index 5fbc308..2a6977c 100644
--- a/sbysrc/sby_core.py
+++ b/sbysrc/sby_core.py
@@ -407,6 +407,7 @@ class SbyJob:
                 print("# running in %s/model/" % (self.workdir), file=f)
                 print("read_ilang design%s.il" % ("_nomem" if "_nomem" in model_name else ""), file=f)
                 print("flatten", file=f)
+                print("setundef -undriven -anyseq", file=f)
                 print("setattr -unset keep", file=f)
                 print("delete -output", file=f)
                 print("opt -full", file=f)
@@ -429,6 +430,7 @@ class SbyJob:
                 print("# running in %s/model/" % (self.workdir), file=f)
                 print("read_ilang design_nomem.il", file=f)
                 print("flatten", file=f)
+                print("setundef -undriven -anyseq", file=f)
                 print("setattr -unset keep", file=f)
                 print("delete -output", file=f)
                 print("opt -full", file=f)
@@ -436,8 +438,6 @@ class SbyJob:
                 print("opt -fast", file=f)
                 print("abc -g AND -fast", file=f)
                 print("opt_clean", file=f)
-                print("setundef -anyseq", file=f)
-                print("opt_clean", file=f)
                 print("stat", file=f)
                 print("write_aiger -I -B -zinit -map design_aiger.aim design_aiger.aig", file=f)