diff --git a/src/mame/drivers/bottom9.c b/src/mame/drivers/bottom9.c
index dfbd9dd41dc..5ffa71f8c99 100644
--- a/src/mame/drivers/bottom9.c
+++ b/src/mame/drivers/bottom9.c
@@ -258,6 +258,12 @@ INPUT_PORTS_END
 static INPUT_PORTS_START( mstadium )
 	PORT_INCLUDE( bottom9 )
 
+	PORT_MODIFY("P1")
+	KONAMI8_ALT_B123(1)
+
+	PORT_MODIFY("P2")
+	KONAMI8_ALT_B123(2)
+
 	PORT_MODIFY("DSW2")
 	PORT_DIPNAME( 0x03, 0x01, "Play Inning" ) PORT_DIPLOCATION("SW2:1,2")
 	PORT_DIPSETTING(    0x03, "1" )