diff --git a/src/mame/drivers/slapshot.c b/src/mame/drivers/slapshot.c
index 32ac9e61877..3173bee068f 100644
--- a/src/mame/drivers/slapshot.c
+++ b/src/mame/drivers/slapshot.c
@@ -567,6 +567,7 @@ static MACHINE_CONFIG_START( opwolf3, slapshot_state )
 
 	MCFG_GFXDECODE_ADD("gfxdecode", "palette", slapshot)
 	MCFG_PALETTE_ADD("palette", 8192)
+	MCFG_PALETTE_FORMAT(XRGB)
 
 	MCFG_DEVICE_ADD("tc0480scp", TC0480SCP, 0)
 	MCFG_TC0480SCP_GFX_REGION(1)
diff --git a/src/mame/drivers/undrfire.c b/src/mame/drivers/undrfire.c
index c189d289968..952491181a6 100644
--- a/src/mame/drivers/undrfire.c
+++ b/src/mame/drivers/undrfire.c
@@ -740,6 +740,7 @@ static MACHINE_CONFIG_START( cbombers, undrfire_state )
 
 	MCFG_GFXDECODE_ADD("gfxdecode", "palette", cbombers)
 	MCFG_PALETTE_ADD("palette", 16384)
+	MCFG_PALETTE_FORMAT(XRGB)
 
 	MCFG_DEVICE_ADD("tc0100scn", TC0100SCN, 0)
 	MCFG_TC0100SCN_GFX_REGION(2)