diff --git a/modules/map/src/mapsys.h b/modules/map/src/mapsys.h
index 2f6291c4d7..e8966d6d0e 100644
--- a/modules/map/src/mapsys.h
+++ b/modules/map/src/mapsys.h
@@ -33,7 +33,7 @@
 
 
 #if defined(_WIN32) || defined(_WIN64)
-#  include <Windows.h>
+#  include <windows.h>
 #  include <tchar.h>
 #else
 #  include <unistd.h>