diff --git a/pomodoro_to_harvest.py b/pomodoro_to_harvest.py
index bf21582..48b30c9 100644
--- a/pomodoro_to_harvest.py
+++ b/pomodoro_to_harvest.py
@@ -76,6 +76,7 @@ for preferred, alternatives in replacement_project_names.items():
 
 # Condense duplicate entries by date, summing the minutes spent, and listing
 # the first started and last recorded times for each task.
+# The fillna is essential or we drop entries with blank ('None') projects.
 tl = timelog.groupby(["date", timelog.project.fillna(""), "description"]).agg({"time": 'sum', "started": 'min', "recorded": 'max'}).reset_index()
 
 tl.to_csv('harvest-ready.csv', index = False)