diff --git a/python/pmtiles/tile.py b/python/pmtiles/tile.py
index aa3397f..0143256 100644
--- a/python/pmtiles/tile.py
+++ b/python/pmtiles/tile.py
@@ -274,13 +274,13 @@ def serialize_header(h):
     write_uint8(h["tile_type"].value)
     write_uint8(h["min_zoom"])
     write_uint8(h["max_zoom"])
-    min_lon_e7 = h.get("min_lon_e7",-180)
+    min_lon_e7 = h.get("min_lon_e7", int(-180 * 10000000))
     write_int32(min_lon_e7)
-    min_lat_e7 = h.get("min_lat_e7",-90)
+    min_lat_e7 = h.get("min_lat_e7", int(-90 * 10000000))
     write_int32(min_lat_e7)
-    max_lon_e7 = h.get("max_lon_e7",180)
+    max_lon_e7 = h.get("max_lon_e7", int(180 * 10000000))
     write_int32(max_lon_e7)
-    max_lat_e7 = h.get("max_lat_e7",90)
+    max_lat_e7 = h.get("max_lat_e7", int(90 * 10000000))
     write_int32(max_lat_e7)
     write_uint8(h.get("center_zoom",h["min_zoom"]))
     write_int32(h.get("center_lon_e7", round((min_lon_e7 + max_lon_e7) / 2)))