diff --git a/src/mame/drivers/hh_sm510.cpp b/src/mame/drivers/hh_sm510.cpp
index 0777707c48e..8610c36b809 100644
--- a/src/mame/drivers/hh_sm510.cpp
+++ b/src/mame/drivers/hh_sm510.cpp
@@ -1694,8 +1694,8 @@ public:
 
 static INPUT_PORTS_START( gnw_lboat )
 	PORT_START("IN.0") // S1
-	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_JOYSTICK_LEFT ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
-	PORT_BIT( 0x02, IP_ACTIVE_HIGH, IPT_JOYSTICK_RIGHT ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr)
+	PORT_BIT( 0x01, IP_ACTIVE_HIGH, IPT_JOYSTICK_LEFT ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_16WAY
+	PORT_BIT( 0x02, IP_ACTIVE_HIGH, IPT_JOYSTICK_RIGHT ) PORT_CHANGED_MEMBER(DEVICE_SELF, hh_sm510_state, input_changed, nullptr) PORT_16WAY
 	PORT_BIT( 0x04, IP_ACTIVE_HIGH, IPT_UNUSED )
 	PORT_BIT( 0x08, IP_ACTIVE_HIGH, IPT_UNUSED )