1 files changed, 1 insertions, 1 deletions
diff --git a/monitor.c b/monitor.c
index 301bde0736..342af32326 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1161,7 +1161,7 @@ static void do_ioport_read(Monitor *mon, int count, int format, int size,
     int suffix;
 
     if (has_index) {
-        cpu_outb(NULL, addr & 0xffff, index & 0xff);
+        cpu_outb(NULL, addr & IOPORTS_MASK, index & 0xff);
         addr++;
     }
     addr &= 0xffff;