diff --git a/hw/smc91c111.c b/hw/smc91c111.c
index a2ef299..e4a2447 100644
--- a/hw/smc91c111.c
+++ b/hw/smc91c111.c
@@ -277,6 +277,8 @@ static void smc91c111_writeb(void *opaque, target_phys_addr_t offset,
         case 10: case 11: /* RPCR */
             /* Ignored */
             return;
+        case 12: case 13: /* Reserved */
+            return;
         }
         break;
 
@@ -463,6 +465,8 @@ static uint32_t smc91c111_readb(void *opaque, target_phys_addr_t offset)
         case 10: case 11: /* RPCR */
             /* Not implemented.  */
             return 0;
+        case 12: case 13: /* Reserved */
+            return 0;
         }
         break;