diff --git a/coconut/compiler/util.py b/coconut/compiler/util.py
index c1fd1cda..d146f7e9 100644
--- a/coconut/compiler/util.py
+++ b/coconut/compiler/util.py
@@ -462,6 +462,7 @@ class CombineToNode(Combine, pickleable_obj):
     """Modified Combine to work with the computation graph."""
     __slots__ = ()
     validation_dict = None
+    pickling_enabled = False
 
     def _combine(self, original, loc, tokens):
         """Implement the parse action for Combine."""
@@ -475,25 +476,23 @@ def postParse(self, original, loc, tokens):
         """Create a ComputationNode for Combine."""
         return ComputationNode(self._combine, original, loc, tokens, ignore_no_tokens=True, ignore_one_token=True, trim_arity=False)
 
-    @classmethod
-    def reconstitute(self, identifier):
-        return identifier_to_parse_elem(identifier, self.validation_dict)
-
     def __reduce__(self):
-        if self.validation_dict is None:
-            return super(CombineToNode, self).__reduce__()
+        if self.pickling_enabled:
+            return (identifier_to_parse_elem, (parse_elem_to_identifier(self, self.validation_dict),))
         else:
-            return (self.reconstitute, (parse_elem_to_identifier(self, self.validation_dict),))
+            return super(CombineToNode, self).__reduce__()
 
     @classmethod
     @contextmanager
-    def enable_pickling(validation_dict={}):
+    def enable_pickling(cls, validation_dict=None):
         """Context manager to enable pickling for CombineToNode."""
-        old_validation_dict, CombineToNode.validation_dict = CombineToNode.validation_dict, validation_dict
+        old_validation_dict, cls.validation_dict = cls.validation_dict, validation_dict
+        old_pickling_enabled, cls.pickling_enabled = cls.pickling_enabled, True
         try:
             yield
         finally:
-            CombineToNode.validation_dict = old_validation_dict
+            cls.pickling_enabled = old_pickling_enabled
+            cls.validation_dict = old_validation_dict
 
 
 if USE_COMPUTATION_GRAPH: