--- src/kernel/sel4/include/plat/pc99/plat/machine/acpi.h
+++ src/kernel/sel4/include/plat/pc99/plat/machine/acpi.h
@@ -15,6 +15,11 @@
 #include <config.h>
 #include <types.h>
 
+enum acpi_size {
+    ACPI_V1_SIZE = 20,
+    ACPI_V2_SIZE = 36
+};
+
 /* Generic System Descriptor Table Header */
 typedef struct acpi_header {
     char         signature[4];
@@ -40,7 +45,7 @@ typedef struct acpi_rsdp {
     uint8_t      extended_checksum;
     char         reserved[3];
 } PACKED acpi_rsdp_t;
-compile_assert(acpi_rsdp_packed, sizeof(acpi_rsdp_t) == 36)
+compile_assert(acpi_rsdp_packed, sizeof(acpi_rsdp_t) == ACPI_V2_SIZE)
 
 /* Root System Descriptor Table */
 typedef struct acpi_rsdt {
--- src/kernel/sel4/src/arch/x86/kernel/boot_sys.c
+++ src/kernel/sel4/src/arch/x86/kernel/boot_sys.c
@@ -651,12 +651,14 @@ try_boot_sys_mbi2(
         if (tag->type == MULTIBOOT2_TAG_CMDLINE) {
             char const * const cmdline = (char const * const)(behind_tag);
             cmdline_parse(cmdline, &cmdline_opt);
-        } else if (tag->type == MULTIBOOT2_TAG_ACPI) {
-            if (sizeof(boot_state.acpi_rsdp) != tag->size - sizeof(*tag)) {
-                printf("sizeof ACPI RSDP unexpected %ld!=%lu\n", (long)sizeof(boot_state.acpi_rsdp), (long)tag->size - sizeof(*tag));
-                return false;
+        } else if (tag->type == MULTIBOOT2_TAG_ACPI_1) {
+            if (ACPI_V1_SIZE == tag->size - sizeof(*tag)) {
+                memcpy(&boot_state.acpi_rsdp, (void *)behind_tag, tag->size - sizeof(*tag));
+            }
+        } else if (tag->type == MULTIBOOT2_TAG_ACPI_2) {
+            if (sizeof(boot_state.acpi_rsdp) == tag->size - sizeof(*tag)) {
+                memcpy(&boot_state.acpi_rsdp, (void *)behind_tag, sizeof(boot_state.acpi_rsdp));
             }
-            memcpy(&boot_state.acpi_rsdp, (void *)behind_tag, sizeof(boot_state.acpi_rsdp));
         } else if (tag->type == MULTIBOOT2_TAG_MODULE) {
             multiboot2_module_t const * module = (multiboot2_module_t const *)behind_tag;
             printf(
--- src/kernel/sel4/src/plat/pc99/machine/acpi.c
+++ src/kernel/sel4/src/plat/pc99/machine/acpi.c
@@ -182,7 +182,7 @@ acpi_get_rsdp(void)
 
     for (addr = (char*)BIOS_PADDR_START; addr < (char*)BIOS_PADDR_END; addr += 16) {
         if (strncmp(addr, acpi_str_rsd, 8) == 0) {
-            if (acpi_calc_checksum(addr, 20) == 0) {
+            if (acpi_calc_checksum(addr, ACPI_V1_SIZE) == 0) {
                 return (acpi_rsdp_t*)addr;
             }
         }
@@ -255,8 +255,13 @@ acpi_validate_rsdp(acpi_rsdp_t *acpi_rsdp)
     acpi_rsdt_t* acpi_rsdt;
     acpi_rsdt_t* acpi_rsdt_mapped;
 
-    if (acpi_calc_checksum((char*)acpi_rsdp, 20) != 0) {
-        printf("BIOS: ACPI information corrupt\n");
+    if (acpi_calc_checksum((char*)acpi_rsdp, ACPI_V1_SIZE) != 0) {
+        printf("BIOS: ACPIv1 information corrupt\n");
+        return false;
+    }
+
+    if (acpi_rsdp->revision > 0 && acpi_calc_checksum((char*)acpi_rsdp, sizeof(*acpi_rsdp)) != 0) {
+        printf("BIOS: ACPIv2 information corrupt\n");
         return false;
     }
 
--- src/kernel/sel4/include/arch/x86/arch/kernel/multiboot2.h
+++ src/kernel/sel4/include/arch/x86/arch/kernel/multiboot2.h
@@ -43,7 +43,8 @@ enum multiboot2_tags {
     MULTIBOOT2_TAG_CMDLINE = 1,
     MULTIBOOT2_TAG_MODULE  = 3,
     MULTIBOOT2_TAG_MEMORY  = 6,
-    MULTIBOOT2_TAG_ACPI    = 15,
+    MULTIBOOT2_TAG_ACPI_1  = 14,
+    MULTIBOOT2_TAG_ACPI_2  = 15,
 };
 
 #endif