diff --git a/th04/formats/map.inc b/th04/formats/map.inc
index 69413eae..e2fb300b 100644
--- a/th04/formats/map.inc
+++ b/th04/formats/map.inc
@@ -2,5 +2,7 @@
 
 map_header_t struc
 	map_size dw ?
-	map_unk dw 3 dup (?)
+	; Number of 25×5 tile sections in this .MAP
+	map_section_count	dw ?
+	map_unk dw 2 dup (?)
 map_header_t ends