diff --git a/newgrf.c b/newgrf.c
--- a/newgrf.c
+++ b/newgrf.c
@@ -31,7 +31,7 @@ GRFFile *_first_grffile;
 int _grffile_count;
 static int _cur_spriteid;
 static int _cur_stage;
-extern int _custom_sprites_base;
+extern uint16 _custom_sprites_base;
 
 static int32 _paramlist[0x7f];
 static int _param_max;