diff --git a/src/mame/drivers/hng64.c b/src/mame/drivers/hng64.c
index 9d5e5152604..05558cd0ebc 100644
--- a/src/mame/drivers/hng64.c
+++ b/src/mame/drivers/hng64.c
@@ -1040,8 +1040,8 @@ static INPUT_PORTS_START( hng64 )
 
 	PORT_START("SYSTEM")
 	PORT_BIT( 0x0000ffff, IP_ACTIVE_HIGH, IPT_UNKNOWN )
-	PORT_BIT( 0x00010000, IP_ACTIVE_HIGH, IPT_COIN1 )
-	PORT_BIT( 0x00020000, IP_ACTIVE_HIGH, IPT_COIN2 )
+	PORT_BIT( 0x00010000, IP_ACTIVE_HIGH, IPT_COIN1 ) PORT_IMPULSE(1)
+	PORT_BIT( 0x00020000, IP_ACTIVE_HIGH, IPT_COIN2 ) PORT_IMPULSE(1)
 	PORT_BIT( 0x00040000, IP_ACTIVE_HIGH, IPT_UNKNOWN )
 	PORT_BIT( 0x00080000, IP_ACTIVE_HIGH, IPT_UNKNOWN )
 	PORT_BIT( 0x00100000, IP_ACTIVE_HIGH, IPT_UNKNOWN )
@@ -1234,9 +1234,9 @@ static INPUT_PORTS_START( bbust2 )
 
 	PORT_START("D_IN")
 	PORT_BIT( 0x000000ff, IP_ACTIVE_HIGH, IPT_UNUSED )
-	PORT_BIT( 0x00000100, IP_ACTIVE_HIGH, IPT_COIN1 )
-	PORT_BIT( 0x00000200, IP_ACTIVE_HIGH, IPT_COIN2 )
-	PORT_BIT( 0x00000400, IP_ACTIVE_HIGH, IPT_COIN3 )
+	PORT_BIT( 0x00000100, IP_ACTIVE_HIGH, IPT_COIN1 ) PORT_IMPULSE(1)
+	PORT_BIT( 0x00000200, IP_ACTIVE_HIGH, IPT_COIN2 ) PORT_IMPULSE(1)
+	PORT_BIT( 0x00000400, IP_ACTIVE_HIGH, IPT_COIN3 ) PORT_IMPULSE(1)
 	PORT_BIT( 0x00000800, IP_ACTIVE_HIGH, IPT_UNUSED )
 	PORT_BIT( 0x00001000, IP_ACTIVE_HIGH, IPT_SERVICE1 )
 	PORT_BIT( 0x00002000, IP_ACTIVE_HIGH, IPT_SERVICE2 )