diff --git a/src/mame/drivers/midyunit.c b/src/mame/drivers/midyunit.c
index 142954fd519..f885a9daf88 100644
--- a/src/mame/drivers/midyunit.c
+++ b/src/mame/drivers/midyunit.c
@@ -742,6 +742,12 @@ static INPUT_PORTS_START( mkla4 )
 	PORT_BIT( 0xffff, IP_ACTIVE_LOW, IPT_UNKNOWN )
 INPUT_PORTS_END
 
+static INPUT_PORTS_START( mkyawdim )
+	PORT_INCLUDE( mkla4 )
+
+	PORT_MODIFY("IN1")
+	PORT_BIT( 0x4000, IP_ACTIVE_LOW, IPT_UNUSED ) // no ADPCM in these bootlegs
+INPUT_PORTS_END
 
 static INPUT_PORTS_START( term2 )
 	PORT_START("IN0")
@@ -2747,8 +2753,8 @@ GAME( 1992, mkyturbo, mk,       yunit_adpcm_6bit_fast,   mkla4,    mkyturbo, ROT
 GAME( 1992, mkyturboe,mk,       yunit_adpcm_6bit_fast,   mkla4,    mkyturbo, ROT0, "hack",     "Mortal Kombat (Turbo 3.0 08/31/92, hack)", GAME_SUPPORTS_SAVE )
 GAME( 1992, mknifty,  mk,       yunit_adpcm_6bit_fast,   mkla4,    mkyturbo, ROT0, "hack",     "Mortal Kombat (Nifty Kombo, hack)", GAME_SUPPORTS_SAVE )
 GAME( 1992, mknifty666, mk,     yunit_adpcm_6bit_fast,   mkla4,    mkyturbo, ROT0, "hack",     "Mortal Kombat (Nifty Kombo 666, hack)", GAME_SUPPORTS_SAVE )
-GAME( 1992, mkyawdim, mk,       mkyawdim,                mkla4,    mkyawdim, ROT0, "bootleg (Yawdim)", "Mortal Kombat (Yawdim bootleg, set 1)", GAME_SUPPORTS_SAVE )
-GAME( 1992, mkyawdim2,mk,       mkyawdim,                mkla4,    mkyawdim, ROT0, "bootleg (Yawdim)", "Mortal Kombat (Yawdim bootleg, set 2)", GAME_SUPPORTS_SAVE | GAME_NO_SOUND )
+GAME( 1992, mkyawdim, mk,       mkyawdim,                mkyawdim, mkyawdim, ROT0, "bootleg (Yawdim)", "Mortal Kombat (Yawdim bootleg, set 1)", GAME_SUPPORTS_SAVE )
+GAME( 1992, mkyawdim2,mk,       mkyawdim,                mkyawdim, mkyawdim, ROT0, "bootleg (Yawdim)", "Mortal Kombat (Yawdim bootleg, set 2)", GAME_SUPPORTS_SAVE | GAME_NO_SOUND )
 
 GAME( 1992, totcarn,  0,        yunit_adpcm_6bit_fast,   totcarn,  totcarn,  ROT0, "Midway",   "Total Carnage (rev LA1 03/10/92)", GAME_SUPPORTS_SAVE )
 GAME( 1992, totcarnp, totcarn,  yunit_adpcm_6bit_fast,   totcarn,  totcarn,  ROT0, "Midway",   "Total Carnage (prototype, rev 1.0 01/25/92)", GAME_SUPPORTS_SAVE )