Index: mame/drivers/cninja.c
===================================================================
--- mame/drivers/cninja.c	(revision 15164)
+++ mame/drivers/cninja.c	(working copy)
@@ -1076,6 +1076,9 @@
 
 	MCFG_TIMER_ADD("raster_timer", interrupt_gen)
 
+	// to force a partial update every line, fixes clouds in 2nd attract demo
+	MCFG_TIMER_ADD_SCANLINE("scantimer", deco16_scantimer, "screen", 0, 1)
+
 	/* video hardware */
 	MCFG_VIDEO_ATTRIBUTES(VIDEO_BUFFERS_SPRITERAM)
 
Index: mame/video/deco16ic.c
===================================================================
--- mame/video/deco16ic.c	(revision 15164)
+++ mame/video/deco16ic.c	(working copy)
@@ -345,6 +345,13 @@
 			flags);
 }
 
+TIMER_DEVICE_CALLBACK( deco16_scantimer )
+{
+	int scanline = param;
+	timer.machine().primary_screen->update_partial(scanline);
+}
+
+
 /*****************************************************************************************/
 
 /*
Index: mame/video/deco16ic.h
===================================================================
--- mame/video/deco16ic.h	(revision 15164)
+++ mame/video/deco16ic.h	(working copy)
@@ -96,4 +96,6 @@
 /* used by cninjabl */
 void deco16ic_set_enable( device_t *device, int tmap, int enable );
 
+TIMER_DEVICE_CALLBACK( deco16_scantimer );
+
 #endif