diff --git a/src/mess/drivers/casloopy.c b/src/mess/drivers/casloopy.c
index 081115970dd..5cb18a2ca98 100644
--- a/src/mess/drivers/casloopy.c
+++ b/src/mess/drivers/casloopy.c
@@ -186,7 +186,7 @@ public:
 	DECLARE_READ8_MEMBER(casloopy_bitmap_r);
 	DECLARE_WRITE8_MEMBER(casloopy_bitmap_w);
 	required_device<cpu_device> m_maincpu;
-	optional_device<gfxdecode_device> m_gfxdecode;
+	required_device<gfxdecode_device> m_gfxdecode;
 };
 
 
@@ -492,6 +492,8 @@ static MACHINE_CONFIG_START( casloopy, casloopy_state )
 	MCFG_SCREEN_UPDATE_DRIVER(casloopy_state, screen_update_casloopy)
 
 	MCFG_PALETTE_LENGTH(512)
+	
+	MCFG_GFXDECODE_ADD("gfxdecode", empty)
 
 	MCFG_CARTSLOT_ADD("cart")
 	MCFG_CARTSLOT_EXTENSION_LIST("ic1,bin")
diff --git a/src/mess/drivers/smc777.c b/src/mess/drivers/smc777.c
index c1d17d6f447..fd9c0d4a10c 100644
--- a/src/mess/drivers/smc777.c
+++ b/src/mess/drivers/smc777.c
@@ -126,7 +126,7 @@ public:
 	DECLARE_WRITE_LINE_MEMBER(smc777_fdc_intrq_w);
 	DECLARE_WRITE_LINE_MEMBER(smc777_fdc_drq_w);
 	void check_floppy_inserted();
-	optional_device<gfxdecode_device> m_gfxdecode;
+	required_device<gfxdecode_device> m_gfxdecode;
 };
 
 
@@ -1090,6 +1090,8 @@ static MACHINE_CONFIG_START( smc777, smc777_state )
 
 	MCFG_PALETTE_LENGTH(0x20) // 16 + 8 colors (SMC-777 + SMC-70) + 8 empty entries (SMC-70)
 
+	MCFG_GFXDECODE_ADD("gfxdecode", empty)
+	
 	MCFG_MC6845_ADD("crtc", H46505, "screen", MASTER_CLOCK/2, mc6845_intf)    /* unknown clock, hand tuned to get ~60 fps */
 
 	MCFG_MB8876_ADD("fdc",smc777_mb8876_interface)