diff --git a/src/mame/includes/dc.h b/src/mame/includes/dc.h
index 1dade3c1212..e7f85f620f3 100644
--- a/src/mame/includes/dc.h
+++ b/src/mame/includes/dc.h
@@ -53,7 +53,7 @@ class dc_state : public driver_device
 		uint8_t indirect;
 		uint8_t start;
 		uint8_t sel;
-	}m_g2_dma[4];
+	} m_g2_dma[4];
 
 	virtual void machine_start() override;
 	virtual void machine_reset() override;
@@ -84,6 +84,7 @@ class dc_state : public driver_device
 	DECLARE_WRITE16_MEMBER( soundram_w );
 	DECLARE_WRITE_LINE_MEMBER(aica_irq);
 	DECLARE_WRITE_LINE_MEMBER(sh4_aica_irq);
+	DECLARE_WRITE_LINE_MEMBER(external_irq);
 
 
 	required_device<sh4_base_device> m_maincpu;
diff --git a/src/mame/machine/dc.cpp b/src/mame/machine/dc.cpp
index 3fb65d363b4..c81382b5661 100644
--- a/src/mame/machine/dc.cpp
+++ b/src/mame/machine/dc.cpp
@@ -748,6 +748,16 @@ WRITE_LINE_MEMBER(dc_state::sh4_aica_irq)
 	dc_update_interrupt_status();
 }
 
+WRITE_LINE_MEMBER(dc_state::external_irq)
+{
+	if (state)
+		dc_sysctrl_regs[SB_ISTEXT] |= IST_EXT_EXTERNAL;
+	else
+		dc_sysctrl_regs[SB_ISTEXT] &= ~IST_EXT_EXTERNAL;
+
+	dc_update_interrupt_status();
+}
+
 MACHINE_RESET_MEMBER(dc_state,dc_console)
 {
 	dc_state::machine_reset();