diff --git a/hw/sun4m.c b/hw/sun4m.c
index 79130c13da..201797b331 100644
--- a/hw/sun4m.c
+++ b/hw/sun4m.c
@@ -258,12 +258,15 @@ void cpu_check_irqs(CPUState *env)
                 int old_interrupt = env->interrupt_index;
 
                 env->interrupt_index = TT_EXTINT | i;
-                if (old_interrupt != env->interrupt_index)
+                if (old_interrupt != env->interrupt_index) {
+                    DPRINTF("Set CPU IRQ %d\n", i);
                     cpu_interrupt(env, CPU_INTERRUPT_HARD);
+                }
                 break;
             }
         }
     } else if (!env->pil_in && (env->interrupt_index & ~15) == TT_EXTINT) {
+        DPRINTF("Reset CPU IRQ %d\n", env->interrupt_index & 15);
         env->interrupt_index = 0;
         cpu_reset_interrupt(env, CPU_INTERRUPT_HARD);
     }