diff --git a/mlonmcu/session/postprocess/postprocesses.py b/mlonmcu/session/postprocess/postprocesses.py
index f988dd39..72b8ada0 100644
--- a/mlonmcu/session/postprocess/postprocesses.py
+++ b/mlonmcu/session/postprocess/postprocesses.py
@@ -1027,7 +1027,7 @@ def post_session(self, report):
         post_df = report.post_df
         group_by = self.group_by
         if group_by is None:
-            group_by = [x for x in pre_df.columns if x != "Run"]
+            group_by = [x for x in pre_df.columns if x not in ["Run", "Sub"]]
         assert isinstance(group_by, list)
         assert all(col in list(pre_df.columns) + list(post_df.columns) for col in group_by), "Cols mssing in df"
         to_compare = self.to_compare