diff --git a/hw/lan9118.c b/hw/lan9118.c
index f8149e6..65096d4 100644
--- a/hw/lan9118.c
+++ b/hw/lan9118.c
@@ -977,6 +977,15 @@ static void lan9118_writel(void *opaque, target_phys_addr_t offset,
         s->pmt_ctrl &= ~0x34e;
         s->pmt_ctrl |= (val & 0x34e);
         break;
+    case CSR_BYTE_TEST:
+        /* Even if this register is marked ReadOnly in the datasheet,
+           a write to this register will wake up the device when 
+           PM_MODE is currently in D1 or D2 mode.
+
+           As Power Modes are not handled in this driver, we will 
+           leave this case with no implementation.
+         */
+        break;
     case CSR_GPIO_CFG:
         /* Probably just enabling LEDs.  */
         s->gpio_cfg = val & 0x7777071f;