diff --git a/hw/acpi/core.c b/hw/acpi/core.c
index f6d9ec4f13..ac06db3450 100644
--- a/hw/acpi/core.c
+++ b/hw/acpi/core.c
@@ -458,7 +458,8 @@ static void acpi_pm_evt_write(void *opaque, hwaddr addr, uint64_t val,
 static const MemoryRegionOps acpi_pm_evt_ops = {
     .read = acpi_pm_evt_read,
     .write = acpi_pm_evt_write,
-    .valid.min_access_size = 2,
+    .impl.min_access_size = 2,
+    .valid.min_access_size = 1,
     .valid.max_access_size = 2,
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
@@ -527,7 +528,8 @@ static void acpi_pm_tmr_write(void *opaque, hwaddr addr, uint64_t val,
 static const MemoryRegionOps acpi_pm_tmr_ops = {
     .read = acpi_pm_tmr_read,
     .write = acpi_pm_tmr_write,
-    .valid.min_access_size = 4,
+    .impl.min_access_size = 4,
+    .valid.min_access_size = 1,
     .valid.max_access_size = 4,
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
@@ -599,7 +601,8 @@ static void acpi_pm_cnt_write(void *opaque, hwaddr addr, uint64_t val,
 static const MemoryRegionOps acpi_pm_cnt_ops = {
     .read = acpi_pm_cnt_read,
     .write = acpi_pm_cnt_write,
-    .valid.min_access_size = 2,
+    .impl.min_access_size = 2,
+    .valid.min_access_size = 1,
     .valid.max_access_size = 2,
     .endianness = DEVICE_LITTLE_ENDIAN,
 };