diff --git a/pytorch3d/implicitron/tools/config.py b/pytorch3d/implicitron/tools/config.py
index 3c2c4d88..0883ca76 100644
--- a/pytorch3d/implicitron/tools/config.py
+++ b/pytorch3d/implicitron/tools/config.py
@@ -11,7 +11,7 @@ import itertools
 import warnings
 from collections import Counter, defaultdict
 from enum import Enum
-from typing import Any, Callable, Dict, List, Optional, Set, Tuple, Type, TypeVar, Union
+from typing import Any, Callable, Dict, List, Optional, Tuple, Type, TypeVar, Union
 
 from omegaconf import DictConfig, OmegaConf, open_dict
 from pytorch3d.common.datatypes import get_args, get_origin
@@ -635,7 +635,9 @@ def expand_args_fields(
         - _known_implementations: Dict[str, Type] containing the classes which
             have been found from the registry.
             (used only to raise a warning if it one has been overwritten)
-        - _processed_members: a Set[str] of all the members which have been transformed.
+        - _processed_members: a Dict[str, Any] of all the members which have been
+            transformed, with values giving the types they were declared to have.
+            (E.g. {"x": X} or {"x": Optional[X]} in the cases above.)
 
     Args:
         some_class: the class to be processed
@@ -660,7 +662,7 @@ def expand_args_fields(
     # unused.
     known_implementations: Dict[str, Type] = {}
     # Names of members which have been processed.
-    processed_members: Set[str] = set()
+    processed_members: Dict[str, Any] = {}
 
     # For all bases except ReplaceableBase and Configurable and object,
     # we need to process them before our own processing. This is
@@ -691,6 +693,7 @@ def expand_args_fields(
             to_process.append((name, underlying_type, process_type))
 
     for name, underlying_type, process_type in to_process:
+        processed_members[name] = some_class.__annotations__[name]
         _process_member(
             name=name,
             type_=underlying_type,
@@ -700,7 +703,6 @@ def expand_args_fields(
             _do_not_process=_do_not_process,
             known_implementations=known_implementations,
         )
-        processed_members.add(name)
 
     for key, count in Counter(creation_functions).items():
         if count > 1:
diff --git a/tests/implicitron/test_config.py b/tests/implicitron/test_config.py
index 6f238412..54c9d7f6 100644
--- a/tests/implicitron/test_config.py
+++ b/tests/implicitron/test_config.py
@@ -255,6 +255,8 @@ class TestConfig(unittest.TestCase):
         container_args = get_default_args(Container)
         container = Container(**container_args)
         self.assertIsInstance(container.fruit, Orange)
+        self.assertEqual(Container._processed_members, {"fruit": Fruit})
+        self.assertEqual(container._processed_members, {"fruit": Fruit})
 
         container_defaulted = Container()
         container_defaulted.fruit_Pear_args.n_pips += 4