diff --git a/hw/i386/microvm-dt.c b/hw/i386/microvm-dt.c
index 287818c641..b3049e4f9f 100644
--- a/hw/i386/microvm-dt.c
+++ b/hw/i386/microvm-dt.c
@@ -210,7 +210,7 @@ static void dt_add_isa_rtc(MicrovmMachineState *mms, ISADevice *dev)
 {
     const char compat[] = "motorola,mc146818";
     uint32_t irq = object_property_get_uint(OBJECT(dev), "irq", &error_fatal);
-    hwaddr base = RTC_ISA_BASE;
+    hwaddr base = object_property_get_uint(OBJECT(dev), "iobase", &error_fatal);
     hwaddr size = 8;
     char *nodename;
 
diff --git a/hw/rtc/mc146818rtc.c b/hw/rtc/mc146818rtc.c
index ef9765bb8f..1ebb412479 100644
--- a/hw/rtc/mc146818rtc.c
+++ b/hw/rtc/mc146818rtc.c
@@ -74,6 +74,8 @@
 #define RTC_CLOCK_RATE            32768
 #define UIP_HOLD_LENGTH           (8 * NANOSECONDS_PER_SECOND / 32768)
 
+#define RTC_ISA_BASE 0x70
+
 static void rtc_set_time(RTCState *s);
 static void rtc_update_time(RTCState *s);
 static void rtc_set_cmos(RTCState *s, const struct tm *tm);
@@ -941,7 +943,7 @@ static void rtc_realizefn(DeviceState *dev, Error **errp)
     qemu_register_suspend_notifier(&s->suspend_notifier);
 
     memory_region_init_io(&s->io, OBJECT(s), &cmos_ops, s, "rtc", 2);
-    isa_register_ioport(isadev, &s->io, RTC_ISA_BASE);
+    isa_register_ioport(isadev, &s->io, s->io_base);
 
     /* register rtc 0x70 port for coalesced_pio */
     memory_region_set_flush_coalesced(&s->io);
@@ -950,7 +952,7 @@ static void rtc_realizefn(DeviceState *dev, Error **errp)
     memory_region_add_subregion(&s->io, 0, &s->coalesced_io);
     memory_region_add_coalescing(&s->coalesced_io, 0, 1);
 
-    qdev_set_legacy_instance_id(dev, RTC_ISA_BASE, 3);
+    qdev_set_legacy_instance_id(dev, s->io_base, 3);
 
     object_property_add_tm(OBJECT(s), "date", rtc_get_date);
 
@@ -983,6 +985,7 @@ ISADevice *mc146818_rtc_init(ISABus *bus, int base_year, qemu_irq intercept_irq)
 
 static Property mc146818rtc_properties[] = {
     DEFINE_PROP_INT32("base_year", RTCState, base_year, 1980),
+    DEFINE_PROP_UINT16("iobase", RTCState, io_base, RTC_ISA_BASE),
     DEFINE_PROP_UINT8("irq", RTCState, isairq, RTC_ISA_IRQ),
     DEFINE_PROP_LOSTTICKPOLICY("lost_tick_policy", RTCState,
                                lost_tick_policy, LOST_TICK_POLICY_DISCARD),
@@ -1028,7 +1031,7 @@ static void rtc_build_aml(AcpiDevAmlIf *adev, Aml *scope)
      * does, even though qemu only responds to the first two ports.
      */
     crs = aml_resource_template();
-    aml_append(crs, aml_io(AML_DECODE16, RTC_ISA_BASE, RTC_ISA_BASE,
+    aml_append(crs, aml_io(AML_DECODE16, s->io_base, s->io_base,
                            0x01, 0x08));
     aml_append(crs, aml_irq_no_flags(s->isairq));
 
diff --git a/include/hw/rtc/mc146818rtc.h b/include/hw/rtc/mc146818rtc.h
index 33d85753c0..1db0fcee92 100644
--- a/include/hw/rtc/mc146818rtc.h
+++ b/include/hw/rtc/mc146818rtc.h
@@ -26,6 +26,7 @@ struct RTCState {
     uint8_t cmos_data[128];
     uint8_t cmos_index;
     uint8_t isairq;
+    uint16_t io_base;
     int32_t base_year;
     uint64_t base_rtc;
     uint64_t last_update;
@@ -49,7 +50,6 @@ struct RTCState {
 };
 
 #define RTC_ISA_IRQ 8
-#define RTC_ISA_BASE 0x70
 
 ISADevice *mc146818_rtc_init(ISABus *bus, int base_year,
                              qemu_irq intercept_irq);