diff --git a/pyxtal/interface/ase_opt.py b/pyxtal/interface/ase_opt.py
index c933ae03..faf579d1 100644
--- a/pyxtal/interface/ase_opt.py
+++ b/pyxtal/interface/ase_opt.py
@@ -48,6 +48,7 @@ def handler(signum, frame):
     signal.signal(signal.SIGALRM, handler)
     signal.alarm(timeout)
     #logger.info(f"{label} start calculation")
+    _fmax = 1e+5
 
     try:
     #if True:
@@ -92,7 +93,7 @@ def handler(signum, frame):
     tag = 'False' if struc is None else 'True'
     logger.info(f"Finishing {label} {tag}")
     #signal.alarm(0)  # Cancel the alarm 
-    return struc
+    return struc #, eng, _fmax
 
 class ASE_optimizer:
     """
diff --git a/pyxtal/lego/builder.py b/pyxtal/lego/builder.py
index e6ce63fe..533587a1 100644
--- a/pyxtal/lego/builder.py
+++ b/pyxtal/lego/builder.py
@@ -1009,16 +1009,15 @@ def optimize_xtal(self, xtal, count=0, opt_type='local',
                                      minimizers=minimizers,
                                      filename=filename)
             xtal, xs = result
-            status = xtal.check_validity(self.criteria, verbose=self.verbose)
-            sim1 = self.get_similarity(xtal)
-            #print("after optim", sim1, status)
+            if result is not None:
+                status = xtal.check_validity(self.criteria, verbose=self.verbose)
+                sim1 = self.get_similarity(xtal)
+                #print("after optim", sim1, status)
+            else:
+                xtal, xs, status, sim1 = None, None, False, None
         else:
-            print("Lattice is None", xtal.get_xtal_string())
-            xtal = None
-            xs = None
-            status = False
-            sim1 = None
-            xs = None
+            print("Lattice is None")#, xtal.get_xtal_string())
+            xtal, xs, status, sim1 = None, None, False, None
             #import sys; sys.exit()
 
         if status: