diff --git a/src/mame/drivers/px4.cpp b/src/mame/drivers/px4.cpp
index 2fdc7cff951..0c62cef6176 100644
--- a/src/mame/drivers/px4.cpp
+++ b/src/mame/drivers/px4.cpp
@@ -74,7 +74,7 @@ public:
 		m_frc_value(0), m_frc_latch(0),
 		m_vadr(0), m_yoff(0),
 		m_artdir(0xff), m_artdor(0xff), m_artsr(0), m_artcr(0),
-		m_one_sec_int_enabled(true),
+		m_one_sec_int_enabled(true), m_key_int_enabled(true),
 		m_key_status(0), m_interrupt_status(0),
 		m_time(), m_clock_state(0),
 		m_ear_last_state(0),