diff --git a/transformer_engine/debug/features/utils/__init__.py b/transformer_engine/debug/features/utils/__init__.py
index d691c1828c..c741ad6353 100644
--- a/transformer_engine/debug/features/utils/__init__.py
+++ b/transformer_engine/debug/features/utils/__init__.py
@@ -21,7 +21,13 @@ def get_reduction_params(tensor_name: str, tp_group: torch.distributed.ProcessGr
     reduce_within_microbatch = tensor_name != "weight"
     if tensor_name == "weight":
         if TEDebugState.weight_tensor_tp_group_reduce:
-            reduction_group = tp_group
+            # Do not overwrite with `None`: in torch.distributed collectives
+            # group=None means the default/world process group.
+            if tp_group is not None:
+                reduction_group = tp_group
+            else:
+                # "Reduce in TP group" requested, but TP group is missing.
+                skip_reduction = True
         else:
             skip_reduction = True
     return skip_reduction, reduction_group, reduce_within_microbatch