diff --git a/src/mess/drivers/apple2.c b/src/mess/drivers/apple2.c
index b315ad204cf..b37fe05c9e1 100644
--- a/src/mess/drivers/apple2.c
+++ b/src/mess/drivers/apple2.c
@@ -727,7 +727,7 @@ static MACHINE_CONFIG_DERIVED( apple2e, apple2_common )
 
 	// IIe and later have no physical slot 0, the "language card" is built into the motherboard
 	MCFG_A2BUS_SLOT_REMOVE("sl0")
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl0", A2BUS_LANG, NULL)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl0", A2BUS_LANG, 0)
 
 	MCFG_A2EAUXSLOT_BUS_ADD(AUXSLOT_TAG, "maincpu", a2eauxbus_intf)
 	MCFG_A2EAUXSLOT_SLOT_ADD(AUXSLOT_TAG, "aux", apple2eaux_cards, "ext80")   // default to an extended 80-column card
@@ -787,9 +787,9 @@ static MACHINE_CONFIG_DERIVED( apple2c, apple2ee )
 	MCFG_A2BUS_SLOT_REMOVE("sl7")
 
 	// TODO: populate the IIc's other virtual slots with ONBOARD_ADD
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl1", A2BUS_SSC, NULL)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl2", A2BUS_SSC, NULL)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl6", A2BUS_DISKII, NULL)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl1", A2BUS_SSC, 0)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl2", A2BUS_SSC, 0)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl6", A2BUS_DISKII, 0)
 
 	MCFG_A2EAUXSLOT_SLOT_REMOVE("aux")
 	MCFG_A2EAUXSLOT_BUS_REMOVE(AUXSLOT_TAG)
@@ -802,7 +802,7 @@ MACHINE_CONFIG_END
 static MACHINE_CONFIG_DERIVED( apple2c_iwm, apple2c )
 
 	MCFG_A2BUS_SLOT_REMOVE("sl6")
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl6", A2BUS_IWM_FDC, NULL)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl6", A2BUS_IWM_FDC, 0)
 MACHINE_CONFIG_END
 
 static MACHINE_CONFIG_DERIVED( laser128, apple2c )
@@ -812,13 +812,13 @@ static MACHINE_CONFIG_DERIVED( laser128, apple2c )
 	MCFG_A2BUS_SLOT_REMOVE("sl2")
 	MCFG_A2BUS_SLOT_REMOVE("sl6")
 
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl1", A2BUS_LASER128, NULL)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl2", A2BUS_LASER128, NULL)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl3", A2BUS_LASER128, NULL)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl4", A2BUS_LASER128, NULL)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl5", A2BUS_LASER128, NULL)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl6", A2BUS_IWM_FDC, NULL)     // slots 6 and 7 are hacks for now
-//    MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl7", A2BUS_LASER128, NULL)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl1", A2BUS_LASER128, 0)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl2", A2BUS_LASER128, 0)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl3", A2BUS_LASER128, 0)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl4", A2BUS_LASER128, 0)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl5", A2BUS_LASER128, 0)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl6", A2BUS_IWM_FDC, 0)     // slots 6 and 7 are hacks for now
+//    MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl7", A2BUS_LASER128, 0)
 MACHINE_CONFIG_END
 
 static MACHINE_CONFIG_DERIVED( space84, apple2p )
diff --git a/src/mess/drivers/apple2gs.c b/src/mess/drivers/apple2gs.c
index 8f736f38bdc..07fd780f5a8 100644
--- a/src/mess/drivers/apple2gs.c
+++ b/src/mess/drivers/apple2gs.c
@@ -359,7 +359,7 @@ static MACHINE_CONFIG_START( apple2gs, apple2gs_state )
 
 	/* slot devices */
 	MCFG_A2BUS_BUS_ADD("a2bus", "maincpu", a2bus_intf)
-	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl0", A2BUS_LANG, NULL)
+	MCFG_A2BUS_ONBOARD_ADD("a2bus", "sl0", A2BUS_LANG, 0)
 	MCFG_A2BUS_SLOT_ADD("a2bus", "sl1", apple2_cards, NULL)
 	MCFG_A2BUS_SLOT_ADD("a2bus", "sl2", apple2_cards, NULL)
 	MCFG_A2BUS_SLOT_ADD("a2bus", "sl3", apple2_cards, NULL)