diff --git a/src/benchmarktool/result/xlsx_gen/plot_sheets/helper_sheet.py b/src/benchmarktool/result/xlsx_gen/plot_sheets/helper_sheet.py
index e563cc6..7d9fe13 100644
--- a/src/benchmarktool/result/xlsx_gen/plot_sheets/helper_sheet.py
+++ b/src/benchmarktool/result/xlsx_gen/plot_sheets/helper_sheet.py
@@ -504,6 +504,10 @@ def finalize(self) -> None:
             col += 1
             self.start_cols[sheet] = col
             for setting in range(self.setting_n):
+                # pre-create all columns of the current table block with object dtype.
+                for block_col in range(col, col + 4):
+                    if block_col not in self.content.columns:
+                        self.content[block_col] = None
                 # setting refs
                 self._add_setting_headers(
                     sheet_ref=sheet_ref,
diff --git a/tests/result/xlsx_gen/test_helper_sheet.py b/tests/result/xlsx_gen/test_helper_sheet.py
index 0a1aea7..f2af0a4 100644
--- a/tests/result/xlsx_gen/test_helper_sheet.py
+++ b/tests/result/xlsx_gen/test_helper_sheet.py
@@ -439,14 +439,14 @@ def test_finalize(self):
 
         self.assertDictEqual(self.sheet.float_occur, {"time": [1, 3], "timeout": [2, 4]})
         self.assertEqual(self.sheet.setting_n, 2)
-        pd.testing.assert_frame_equal(
-            self.sheet.content,
-            pd.DataFrame(
-                {
-                    0: pd.Series([None, "time", "timeout"], dtype=object),
-                    1: pd.Series([None, 1.0, 2.0], dtype=object),
-                },
-            ),
+        pd.testing.assert_series_equal(
+            self.sheet.content[0],
+            pd.Series([None, "time", "timeout"], dtype=object, name=0),
+            check_dtype=False,
+        )
+        pd.testing.assert_series_equal(
+            self.sheet.content[1],
+            pd.Series([None, 1.0, 2.0], dtype=object, name=1),
             check_dtype=False,
         )
 
@@ -478,14 +478,14 @@ def test_finalize(self):
 
         self.assertDictEqual(self.sheet.float_occur, {"time": [1], "timeout": [2]})
         self.assertEqual(self.sheet.setting_n, 1)
-        pd.testing.assert_frame_equal(
-            self.sheet.content,
-            pd.DataFrame(
-                {
-                    0: pd.Series([None, "time", "timeout"], dtype=object),
-                    1: pd.Series([None, 1.0, 2.0], dtype=object),
-                },
-            ),
+        pd.testing.assert_series_equal(
+            self.sheet.content[0],
+            pd.Series([None, "time", "timeout"], dtype=object, name=0),
+            check_dtype=False,
+        )
+        pd.testing.assert_series_equal(
+            self.sheet.content[1],
+            pd.Series([None, 1.0, 2.0], dtype=object, name=1),
             check_dtype=False,
         )