diff --git a/timely_beliefs/beliefs/utils.py b/timely_beliefs/beliefs/utils.py
index 1ca3e049..5470d71d 100644
--- a/timely_beliefs/beliefs/utils.py
+++ b/timely_beliefs/beliefs/utils.py
@@ -1067,11 +1067,15 @@ def convert_to_instantaneous(
     """
     df2 = df.copy()
     df2.index = df2.index + df.event_resolution
-    df = df.reset_index().set_index(["event_start", "belief_time", "source", "cumulative_probability"])
-    df2 = df2.reset_index().set_index(["event_start", "belief_time", "source", "cumulative_probability"])
+    df = df.reset_index().set_index(
+        ["event_start", "belief_time", "source", "cumulative_probability"]
+    )
+    df2 = df2.reset_index().set_index(
+        ["event_start", "belief_time", "source", "cumulative_probability"]
+    )
     df = pd.concat([df, df2], axis=1)
     if boundary_policy == "first":
-        s = df.fillna(method='bfill', axis=1).iloc[:, 0]
+        s = df.fillna(method="bfill", axis=1).iloc[:, 0]
     else:
         s = getattr(df, boundary_policy)(axis=1).rename("event_value")
     df = s.sort_index().reset_index().set_index("event_start")
diff --git a/timely_beliefs/tests/test_df_resampling.py b/timely_beliefs/tests/test_df_resampling.py
index 35b24370..8bee0b86 100644
--- a/timely_beliefs/tests/test_df_resampling.py
+++ b/timely_beliefs/tests/test_df_resampling.py
@@ -449,6 +449,6 @@ def test_upsample_to_instantaneous(df_4111, test_source_a: BeliefSource):
     ]
     pd.testing.assert_index_equal(
         df.index.get_level_values(level="event_start"),
-        pd.DatetimeIndex(expected_event_starts, name="event_start")
+        pd.DatetimeIndex(expected_event_starts, name="event_start"),
     )
     assert df["event_value"].values.tolist() == expected_values