diff --git a/src/visualization/heatmap_sensors_per_minute_per_time_segment.py b/src/visualization/heatmap_sensors_per_minute_per_time_segment.py
index bc975da2..5be1b897 100644
--- a/src/visualization/heatmap_sensors_per_minute_per_time_segment.py
+++ b/src/visualization/heatmap_sensors_per_minute_per_time_segment.py
@@ -38,6 +38,7 @@ def getDataForPlot(phone_data_yield_per_segment):
     for columns in columns_for_full_index:
         full_index = full_index + columns
     full_index = pd.MultiIndex.from_tuples(full_index, names=("local_segment_start_datetimes", "minutes_after_segment_start"))
+    phone_data_yield_per_segment = phone_data_yield_per_segment[["local_segment_start_datetimes", "minutes_after_segment_start"]].drop_duplicates(keep="first")
     phone_data_yield_per_segment = phone_data_yield_per_segment.set_index(["local_segment_start_datetimes", "minutes_after_segment_start"]).reindex(full_index).reset_index().fillna(0)
     
     # transpose the dataframe per local start datetime of the segment and discard the useless index layer