diff --git a/src/mess/drivers/c64.c b/src/mess/drivers/c64.c
index 1dab7f4ab2c..14345119482 100644
--- a/src/mess/drivers/c64.c
+++ b/src/mess/drivers/c64.c
@@ -40,7 +40,7 @@
 
 void c64_state::check_interrupts()
 {
-	int restore = !BIT(m_restore->read_safe(0xff), 0);
+	int restore = m_restore ? !BIT(m_restore->read(), 0) : CLEAR_LINE;
 
 	int irq = m_cia1_irq || m_vic_irq || m_exp_irq;
 	int nmi = m_cia2_irq || restore || m_exp_nmi;