diff --git a/python/resdata/summary/rd_sum.py b/python/resdata/summary/rd_sum.py
index 3cc954c69..b644a0bc6 100644
--- a/python/resdata/summary/rd_sum.py
+++ b/python/resdata/summary/rd_sum.py
@@ -13,7 +13,7 @@
 import ctypes
 import pandas as pd
 import re
-from typing import Sequence, List, Tuple, Optional
+from typing import Sequence, List, Tuple, Optional, Union
 
 # Observe that there is some convention conflict with the C code
 # regarding order of arguments: The C code generally takes the time
@@ -477,7 +477,9 @@ def get_values(self, key, report_only=False):
         else:
             raise KeyError("Summary object does not have key:%s" % key)
 
-    def _make_time_vector(self, time_index):
+    def _make_time_vector(
+        self, time_index: Sequence[Union[CTime, datetime.datetime, int, datetime.date]]
+    ) -> TimeVector:
         time_points = TimeVector()
         for t in time_index:
             time_points.append(t)
@@ -558,7 +560,11 @@ def report_dates(self):
                 dates.append(self.get_report_time(report))
         return dates
 
-    def pandas_frame(self, time_index=None, column_keys=None):
+    def pandas_frame(
+        self,
+        time_index: Optional[Sequence[datetime.datetime]] = None,
+        column_keys: Optional[Sequence[str]] = None,
+    ) -> pd.DataFrame:
         """Will create a pandas frame with summary data.
 
         By default you will get all time points in the summary case, but by
@@ -615,8 +621,7 @@ def pandas_frame(self, time_index=None, column_keys=None):
                 data.ctypes.data_as(ctypes.POINTER(ctypes.c_double)),
             )
 
-        frame = pd.DataFrame(index=time_index, columns=list(keywords), data=data)
-        return frame
+        return pd.DataFrame(index=list(time_index), columns=list(keywords), data=data)
 
     @staticmethod
     def _compile_headers_list(
diff --git a/python/tests/rd_tests/test_sum.py b/python/tests/rd_tests/test_sum.py
index 198f4627e..28faf6a86 100644
--- a/python/tests/rd_tests/test_sum.py
+++ b/python/tests/rd_tests/test_sum.py
@@ -2,6 +2,7 @@
 import datetime
 import os
 import os.path
+import pytest
 import shutil
 import stat
 import datetime
@@ -26,6 +27,7 @@ def assert_frame_equal(a, b):
 from resdata.summary import Summary, SummaryKeyWordVector, SummaryVarType
 from resdata.util.test import TestAreaContext
 from resdata.util.test.mock import createSummary
+from resdata.util.util import CTime, TimeVector
 from tests import ResdataTest
 
 
@@ -596,30 +598,6 @@ def test_wells_and_groups(self):
         self.assertEqual(case.wells(), [])
         self.assertEqual(case.groups(), [])
 
-    def test_pandas(self):
-        case = create_case()
-        dates = (
-            [datetime.datetime(2000, 1, 1)]
-            + case.dates
-            + [datetime.datetime(2020, 1, 1)]
-        )
-        frame = case.pandas_frame(column_keys=["FOPT", "FOPR"], time_index=dates)
-
-        fopr = frame["FOPR"]
-        fopt = frame["FOPT"]
-
-        self.assertEqual(fopr[0], 0)
-        self.assertEqual(fopr[-1], 0)
-
-        self.assertEqual(fopt[0], 0)
-        self.assertEqual(fopt[0], case.first_value("FOPT"))
-        self.assertEqual(fopt[-1], case.last_value("FOPT"))
-
-        frame = case.pandas_frame()
-        rows, columns = frame.shape
-        self.assertEqual(len(case.keys()), columns)
-        self.assertEqual(len(case), rows)
-
     def test_csv_load(self):
         case = create_case2()
         frame = case.pandas_frame()
@@ -691,7 +669,6 @@ def test_resample_extrapolate(self):
         """
         Test resampling of summary with extrapolate option of lower and upper boundaries enabled
         """
-        from resdata.util.util import CTime, TimeVector
 
         time_points = TimeVector()
 
@@ -757,6 +734,37 @@ def test_resample_extrapolate(self):
                 )
 
 
+def create_time_vector(lst):
+    vec = TimeVector()
+    for l in lst:
+        vec.append(l)
+    return vec
+
+
+@pytest.mark.parametrize("time_index_type", [list, create_time_vector, tuple])
+def test_summary_to_pandas_frame(time_index_type):
+    case = create_case()
+    dates = time_index_type(
+        [datetime.datetime(2000, 1, 1)] + case.dates + [datetime.datetime(2020, 1, 1)]
+    )
+    frame = case.pandas_frame(column_keys=["FOPT", "FOPR"], time_index=dates)
+
+    fopr = frame["FOPR"]
+    fopt = frame["FOPT"]
+
+    assert fopr[0] == 0
+    assert fopr[-1] == 0
+
+    assert fopt[0] == 0
+    assert fopt[0] == case.first_value("FOPT")
+    assert fopt[-1] == case.last_value("FOPT")
+
+    frame = case.pandas_frame()
+    rows, columns = frame.shape
+    assert len(case.keys()) == columns
+    assert len(case) == rows
+
+
 def test_t_step():
     sum = createSummary(
         "CASE",