diff --git a/src/mame/includes/stv.h b/src/mame/includes/stv.h
index 54670e620fd..df4255f0fd5 100644
--- a/src/mame/includes/stv.h
+++ b/src/mame/includes/stv.h
@@ -92,9 +92,6 @@ public:
 };
 
 
-extern int minit_boost,sinit_boost;
-extern attotime minit_boost_timeslice, sinit_boost_timeslice;
-
 DRIVER_INIT ( stv );
 
 
diff --git a/src/mame/video/deco16ic.c b/src/mame/video/deco16ic.c
index b07bb758da3..83ccaf05912 100644
--- a/src/mame/video/deco16ic.c
+++ b/src/mame/video/deco16ic.c
@@ -398,7 +398,7 @@ static void custom_tilemap_draw(
 
 	width_mask = src_bitmap0->width - 1;
 	height_mask = src_bitmap0->height - 1;
-	src_y = scrolly + starty;
+	src_y = (scrolly + starty) & height_mask;
 
 
 	for (y = starty; y < endy; y++)