diff --git a/hw/rtc/mc146818rtc.c b/hw/rtc/mc146818rtc.c
index fe05a4488e..1e9fa0f33f 100644
--- a/hw/rtc/mc146818rtc.c
+++ b/hw/rtc/mc146818rtc.c
@@ -1013,12 +1013,14 @@ static void rtc_build_aml(ISADevice *isadev, Aml *scope)
     Aml *dev;
     Aml *crs;
 
+    /*
+     * Reserving 8 io ports here, following what physical hardware
+     * 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,
-                           0x10, 0x02));
+                           0x01, 0x08));
     aml_append(crs, aml_irq_no_flags(RTC_ISA_IRQ));
-    aml_append(crs, aml_io(AML_DECODE16, RTC_ISA_BASE + 2, RTC_ISA_BASE + 2,
-                           0x02, 0x06));
 
     dev = aml_device("RTC");
     aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0B00")));