diff --git a/src/mame/drivers/pc9801.cpp b/src/mame/drivers/pc9801.cpp
index 4b771685b4e..90a6665f1f0 100644
--- a/src/mame/drivers/pc9801.cpp
+++ b/src/mame/drivers/pc9801.cpp
@@ -2461,6 +2461,7 @@ MACHINE_CONFIG_START(pc9801_state::pc9801vm)
 	MCFG_DEVICE_REPLACE("maincpu",V30,10000000)
 	MCFG_DEVICE_PROGRAM_MAP(pc9801ux_map)
 	MCFG_DEVICE_IO_MAP(pc9801ux_io)
+	MCFG_DEVICE_IRQ_ACKNOWLEDGE_DEVICE("pic8259_master", pic8259_device, inta_cb)
 
 	MCFG_DEVICE_MODIFY(RAM_TAG)
 	MCFG_RAM_DEFAULT_SIZE("640K")