diff --git a/lib/frequencies.js b/lib/frequencies.js
index f4c8f1e..3ae3e8d 100644
--- a/lib/frequencies.js
+++ b/lib/frequencies.js
@@ -74,13 +74,15 @@ SET frequencies_row = t.frequencies_row
 FROM (
 	SELECT
 		-- order by all columns so that we don't implicitly depend on the file's order
-		(row_number() OVER (PARTITION BY trip_id, exact_times ORDER BY start_time, end_time, headway_secs))::integer AS frequencies_row,
+		(row_number() OVER (PARTITION BY trip_id, start_time ORDER BY end_time, headway_secs, exact_times))::integer AS frequencies_row,
 		trip_id, start_time
 	FROM "${opt.schema}".frequencies
 ) AS t
 -- self-join
+-- frequencies' primary is just (trip_id, start_time)
+-- see also https://github.com/google/transit/issues/514
 WHERE frequencies.trip_id = t.trip_id
-AND frequencies.exact_times = t.exact_times;
+AND frequencies.start_time = t.start_time;
 
 CREATE INDEX ON "${opt.schema}".frequencies (trip_id);
 CREATE INDEX ON "${opt.schema}".frequencies (exact_times);