diff --git a/core/vip.c b/core/vip.c
index 49f12f3..ca4239f 100644
--- a/core/vip.c
+++ b/core/vip.c
@@ -436,6 +436,9 @@ static void vipWriteIO(
 
         case 0x5F802>>1: /* INTENB */
             sim->vip.intenb = (sim->vip.intenb & mask) | (value & 0xE01F);
+            if (sim->vip.intenb & sim->vip.intpnd)
+                sim->cpu.irq  |=  0x0010;
+            else sim->cpu.irq &= ~0x0010;
             break;
         case 0x5F804>>1: /* INTCLR */
             sim->vip.intpnd &= ~value;