diff --git a/torchdistill/core/interfaces/registry.py b/torchdistill/core/interfaces/registry.py
index 4995c9e6..06eb3551 100644
--- a/torchdistill/core/interfaces/registry.py
+++ b/torchdistill/core/interfaces/registry.py
@@ -247,9 +247,7 @@ def get_forward_proc_func(key):
     :return: registered forward process function.
     :rtype: typing.Callable
     """
-    if key is None:
-        return FORWARD_PROC_FUNC_DICT['forward_batch_only']
-    elif key in FORWARD_PROC_FUNC_DICT:
+    if key in FORWARD_PROC_FUNC_DICT:
         return FORWARD_PROC_FUNC_DICT[key]
     raise ValueError('No forward process function `{}` registered'.format(key))