diff --git a/ecell4/util/parseobj.py b/ecell4/util/parseobj.py
index <HASH>..<HASH> 100644
--- a/ecell4/util/parseobj.py
+++ b/ecell4/util/parseobj.py
@@ -485,8 +485,8 @@ class SubExp(ExpBase):
     def __append(self, obj):
         if isinstance(obj, AnyCallable):
             self._elems.append(obj._as_ParseObj())
-        elif len(self._elems) > 0 and isinstance(obj, SubExp):
-            self._elems.extend(obj._elements())
+        # elif len(self._elems) > 0 and isinstance(obj, SubExp):
+        #     self._elems.extend(obj._elements())
         else:
             self._elems.append(obj)
Fix a critical bug related to ode again