diff --git a/etc/db/upgrades/upgrade36-v0.5.3-fix-final_lines_summary-view.sql b/etc/db/upgrades/upgrade36-v0.5.3-fix-final_lines_summary-view.sql
new file mode 100644
index 0000000..441161a
--- /dev/null
+++ b/etc/db/upgrades/upgrade36-v0.5.3-fix-final_lines_summary-view.sql
@@ -0,0 +1,132 @@
+-- Fix final_lines_summary view
+--
+-- New schema version: 0.5.3
+--
+-- ATTENTION:
+--
+-- ENSURE YOU HAVE BACKED UP THE DATABASE BEFORE RUNNING THIS SCRIPT.
+--
+--
+-- NOTE: This upgrade affects all schemas in the database.
+-- NOTE: Each application starts a transaction, which must be committed
+-- or rolled back.
+--
+-- This fixes a long-standing bug, where if the sail and source lines are
+-- the same, the number of missing shots will be miscounted.
+--
+-- This update fixes #313.
+--
+-- To apply, run as the dougal user:
+--
+-- psql <<EOF
+-- \i $THIS_FILE
+-- COMMIT;
+-- EOF
+--
+-- NOTE: It can be applied multiple times without ill effect.
+--
+
+BEGIN;
+
+CREATE OR REPLACE PROCEDURE pg_temp.show_notice (notice text) AS $$
+BEGIN
+	RAISE NOTICE '%', notice;
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE pg_temp.upgrade_survey_schema (schema_name text) AS $outer$
+BEGIN
+
+	RAISE NOTICE 'Updating schema %', schema_name;
+	-- We need to set the search path because some of the trigger
+	-- functions reference other tables in survey schemas assuming
+	-- they are in the search path.
+	EXECUTE format('SET search_path TO %I,public', schema_name);
+
+	CREATE OR REPLACE VIEW final_lines_summary
+	AS
+	WITH summary AS (
+		SELECT DISTINCT fs.sequence,
+			first_value(fs.point) OVER w AS fsp,
+			last_value(fs.point) OVER w AS lsp,
+			first_value(fs.tstamp) OVER w AS ts0,
+			last_value(fs.tstamp) OVER w AS ts1,
+			count(fs.point) OVER w AS num_points,
+			count(pp.point) OVER w AS num_preplots,
+			st_distance(first_value(fs.geometry) OVER w, last_value(fs.geometry) OVER w) AS length,
+			st_azimuth(first_value(fs.geometry) OVER w, last_value(fs.geometry) OVER w) * 180::double precision / pi() AS azimuth
+		FROM final_shots fs
+		LEFT JOIN preplot_points pp USING (line, point)
+		WINDOW w AS (PARTITION BY fs.sequence ORDER BY fs.tstamp ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
+	)
+	SELECT fl.sequence,
+		fl.line,
+		s.fsp,
+		s.lsp,
+		s.ts0,
+		s.ts1,
+		s.ts1 - s.ts0 AS duration,
+		s.num_points,
+		(( SELECT count(*) AS count
+			FROM preplot_points
+			WHERE preplot_points.line = fl.line AND (preplot_points.point >= s.fsp AND preplot_points.point <= s.lsp OR preplot_points.point >= s.lsp AND preplot_points.point <= s.fsp))) - s.num_preplots AS missing_shots,
+		s.length,
+		s.azimuth,
+		fl.remarks,
+		fl.meta
+	FROM summary s
+		JOIN final_lines fl USING (sequence);
+
+	ALTER TABLE final_lines_summary
+		OWNER TO postgres;
+
+END;
+$outer$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE PROCEDURE pg_temp.upgrade () AS $outer$
+DECLARE
+	row RECORD;
+	current_db_version TEXT;
+BEGIN
+
+	SELECT value->>'db_schema' INTO current_db_version FROM public.info WHERE key = 'version';
+
+	IF current_db_version >= '0.5.3' THEN
+		RAISE EXCEPTION
+			USING MESSAGE='Patch already applied';
+	END IF;
+
+	IF current_db_version != '0.5.2' THEN
+		RAISE EXCEPTION
+			USING MESSAGE='Invalid database version: ' || current_db_version,
+				HINT='Ensure all previous patches have been applied.';
+	END IF;
+
+	FOR row IN
+		SELECT schema_name FROM information_schema.schemata
+		WHERE schema_name LIKE 'survey_%'
+		ORDER BY schema_name
+	LOOP
+		CALL pg_temp.upgrade_survey_schema(row.schema_name);
+	END LOOP;
+END;
+$outer$ LANGUAGE plpgsql;
+
+CALL pg_temp.upgrade();
+
+CALL pg_temp.show_notice('Cleaning up');
+DROP PROCEDURE pg_temp.upgrade_survey_schema (schema_name text);
+DROP PROCEDURE pg_temp.upgrade ();
+
+CALL pg_temp.show_notice('Updating db_schema version');
+INSERT INTO public.info VALUES ('version', '{"db_schema": "0.5.3"}')
+ON CONFLICT (key) DO UPDATE
+	SET value = public.info.value || '{"db_schema": "0.5.3"}' WHERE public.info.key = 'version';
+
+
+CALL pg_temp.show_notice('All done. You may now run "COMMIT;" to persist the changes');
+DROP PROCEDURE pg_temp.show_notice (notice text);
+
+--
+--NOTE Run `COMMIT;` now if all went well
+--