diff --git a/hw/sun4u.c b/hw/sun4u.c
index 237e20c1bf..50bc0d2e57 100644
--- a/hw/sun4u.c
+++ b/hw/sun4u.c
@@ -309,19 +309,22 @@ static void cpu_set_ivec_irq(void *opaque, int irq, int level)
     CPUSPARCState *env = opaque;
 
     if (level) {
-        CPUIRQ_DPRINTF("Raise IVEC IRQ %d\n", irq);
-        env->interrupt_index = TT_IVEC;
-        env->pil_in |= 1 << 5;
-        env->ivec_status |= 0x20;
-        env->ivec_data[0] = (0x1f << 6) | irq;
-        env->ivec_data[1] = 0;
-        env->ivec_data[2] = 0;
-        cpu_interrupt(env, CPU_INTERRUPT_HARD);
-      } else {
-        CPUIRQ_DPRINTF("Lower IVEC IRQ %d\n", irq);
-        env->pil_in &= ~(1 << 5);
-        env->ivec_status &= ~0x20;
-        cpu_reset_interrupt(env, CPU_INTERRUPT_HARD);
+        if (!(env->ivec_status & 0x20)) {
+            CPUIRQ_DPRINTF("Raise IVEC IRQ %d\n", irq);
+            env->halted = 0;
+            env->interrupt_index = TT_IVEC;
+            env->ivec_status |= 0x20;
+            env->ivec_data[0] = (0x1f << 6) | irq;
+            env->ivec_data[1] = 0;
+            env->ivec_data[2] = 0;
+            cpu_interrupt(env, CPU_INTERRUPT_HARD);
+        }
+    } else {
+        if (env->ivec_status & 0x20) {
+            CPUIRQ_DPRINTF("Lower IVEC IRQ %d\n", irq);
+            env->ivec_status &= ~0x20;
+            cpu_reset_interrupt(env, CPU_INTERRUPT_HARD);
+        }
     }
 }