diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index b0ecfaca9e..92194a9a53 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2589,7 +2589,7 @@ static void spapr_machine_init(MachineState *machine)
     /* Set up VIO bus */
     spapr->vio_bus = spapr_vio_bus_init();
 
-    for (i = 0; i < MAX_SERIAL_PORTS; i++) {
+    for (i = 0; i < serial_max_hds(); i++) {
         if (serial_hd(i)) {
             spapr_vty_create(spapr->vio_bus, serial_hd(i));
         }
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index 989cbc2b7b..544ab77a2b 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -159,10 +159,12 @@ void hmp_pcie_aer_inject_error(Monitor *mon, const QDict *qdict);
 
 /* serial ports */
 
-#define MAX_SERIAL_PORTS 4
-
 /* Return the Chardev for serial port i, or NULL if none */
 Chardev *serial_hd(int i);
+/* return the number of serial ports defined by the user. serial_hd(i)
+ * will always return NULL for any i which is greater than or equal to this.
+ */
+int serial_max_hds(void);
 
 /* parallel ports */
 
diff --git a/vl.c b/vl.c
index a8a98c5a37..616956adf1 100644
--- a/vl.c
+++ b/vl.c
@@ -2524,6 +2524,11 @@ Chardev *serial_hd(int i)
     return NULL;
 }
 
+int serial_max_hds(void)
+{
+    return num_serial_hds;
+}
+
 static int parallel_parse(const char *devname)
 {
     static int index = 0;