diff --git a/src/pg/sql/45_observatory_mvt.sql b/src/pg/sql/45_observatory_mvt.sql
index 9ba25fe..a81cca7 100644
--- a/src/pg/sql/45_observatory_mvt.sql
+++ b/src/pg/sql/45_observatory_mvt.sql
@@ -12,7 +12,7 @@ def tile2lnglat(z, x, y):
     return lon, lat
 
 lon0, lat0 = tile2lnglat(z, x, y)
-lon1, lat1 = tile2lnglat(z, x+1, y+1)
+lon1, lat1 = tile2lnglat(z, x+1, y-1)
 
 return [lon0, lat0, lon1, lat1]
 $$ LANGUAGE plpythonu;