diff --git a/app/test.h b/app/test.h
index 7267273..904d306 100644
--- a/app/test.h
+++ b/app/test.h
@@ -52,7 +52,7 @@ extern barrier_t *run_barrier;
  */
 extern spinlock_t *error_mutex;
 
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
 /**
  * The word width (in bits) used for memory testing.
  */
diff --git a/boot/efi.h b/boot/efi.h
index 048f9fc..852c62c 100644
--- a/boot/efi.h
+++ b/boot/efi.h
@@ -13,7 +13,7 @@
 
 #include <stdint.h>
 
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
 #define NATIVE_MSB              UINT64_C(0x8000000000000000)
 #else
 #define NATIVE_MSB              0x80000000
@@ -71,7 +71,7 @@
 
 #define efiapi __attribute__((ms_abi))
 
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
 typedef uint64_t        uintn_t;
 #else
 typedef uint32_t        uintn_t;
diff --git a/boot/efisetup.c b/boot/efisetup.c
index 54e8be4..c4bbe69 100644
--- a/boot/efisetup.c
+++ b/boot/efisetup.c
@@ -146,7 +146,7 @@ static void test_frame_buffer(screen_info_t *si)
     pixel_value.word = (r_value << si->red_pos) | (g_value << si->green_pos) | (b_value << si->blue_pos);
 
     uintptr_t lfb_base = si->lfb_base;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     if (LFB_CAPABILITY_64BIT_BASE & si->capabilities) {
         lfb_base |= (uintptr_t)si->ext_lfb_base << 32;
     }
@@ -489,7 +489,7 @@ static efi_status_t set_screen_info_from_gop(screen_info_t *si, efi_handle_t *ha
     si->lfb_width  = best_info.h_resolution;
     si->lfb_height = best_info.v_resolution;
     si->lfb_base   = lfb_base;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     if (lfb_base >> 32) {
         si->capabilities |= LFB_CAPABILITY_64BIT_BASE;
         si->ext_lfb_base = lfb_base >> 32;
@@ -669,7 +669,7 @@ static efi_status_t set_efi_info_and_exit_boot_services(efi_handle_t handle, boo
         goto fail;
     }
 
-#ifdef __x86_64
+#if (ARCH_BITS == 64)
     boot_params->efi_info.loader_signature  = EFI64_LOADER_SIGNATURE;
 #else
     boot_params->efi_info.loader_signature  = EFI32_LOADER_SIGNATURE;
@@ -679,7 +679,7 @@ static efi_status_t set_efi_info_and_exit_boot_services(efi_handle_t handle, boo
     boot_params->efi_info.mem_desc_version  = mem_desc_version;
     boot_params->efi_info.mem_map           = (uintptr_t)mem_map;
     boot_params->efi_info.mem_map_size      = mem_map_size;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     boot_params->efi_info.sys_tab_hi        = (uintptr_t)sys_table >> 32;
     boot_params->efi_info.mem_map_hi        = (uintptr_t)mem_map   >> 32;
 #endif
@@ -691,7 +691,7 @@ fail:
 static void set_e820_map(boot_params_t *params)
 {
     uintptr_t mem_map_addr = params->efi_info.mem_map;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     mem_map_addr |= (uintptr_t)params->efi_info.mem_map_hi << 32;
 #endif
     size_t mem_map_size  = params->efi_info.mem_map_size;
diff --git a/build32/Makefile b/build32/Makefile
index 3033a05..1eb8e1a 100644
--- a/build32/Makefile
+++ b/build32/Makefile
@@ -11,7 +11,7 @@ else
 endif
 
 CFLAGS = -std=gnu11 -Wall -Wextra -Wshadow -m32 -march=i586 -fpic -fno-builtin \
-         -ffreestanding -fomit-frame-pointer -fno-stack-protector
+         -ffreestanding -fomit-frame-pointer -fno-stack-protector -DARCH_BITS=32
 
 ifeq ($(DEBUG), 1)
   CFLAGS+=-ggdb3 -DDEBUG_GDB
diff --git a/build64/Makefile b/build64/Makefile
index 8e2d259..5e68266 100644
--- a/build64/Makefile
+++ b/build64/Makefile
@@ -11,7 +11,8 @@ else
 endif
 
 CFLAGS = -std=gnu11 -Wall -Wextra -Wshadow -m64 -march=x86-64 -mno-mmx -mno-sse -mno-sse2 \
-         -fpic -fno-builtin -ffreestanding -fomit-frame-pointer -fno-stack-protector
+         -fpic -fno-builtin -ffreestanding -fomit-frame-pointer -fno-stack-protector \
+         -DARCH_BITS=64
 
 ifeq ($(DEBUG), 1)
   CFLAGS+=-ggdb3 -DDEBUG_GDB
diff --git a/system/acpi.c b/system/acpi.c
index d81e29e..8abe930 100644
--- a/system/acpi.c
+++ b/system/acpi.c
@@ -100,7 +100,7 @@ static rsdp_t *scan_for_rsdp(uintptr_t addr, int length)
     return NULL;
 }
 
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
 static rsdp_t *find_rsdp_in_efi64_system_table(efi64_system_table_t *system_table)
 {
     efi64_config_table_t *config_tables = (efi64_config_table_t *)map_region(system_table->config_tables,
@@ -150,7 +150,7 @@ static uintptr_t find_rsdp(void)
 
     // Search for the RSDP
     rsdp_t *rp = NULL;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     if (efi_info->loader_signature == EFI64_LOADER_SIGNATURE) {
         uintptr_t system_table_addr = (uintptr_t)efi_info->sys_tab_hi << 32 | (uintptr_t)efi_info->sys_tab;
         system_table_addr = map_region(system_table_addr, sizeof(efi64_system_table_t), true);
@@ -279,7 +279,7 @@ static bool parse_fadt(uintptr_t fadt_addr)
     acpi_config.pm_addr  = *(uint32_t *)(fadt_addr+FADT_PM_TMR_BLK_OFFSET);
     acpi_config.pm_is_io = true;
 
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     acpi_gen_addr_struct *rt;
 
     // Get APIC Timer Address
diff --git a/system/hwctrl.c b/system/hwctrl.c
index 945df87..f04da50 100644
--- a/system/hwctrl.c
+++ b/system/hwctrl.c
@@ -33,7 +33,7 @@ static efi_runtime_services_t   *efi_rs_table = NULL;
 void hwctrl_init(void)
 {
     boot_params_t *boot_params = (boot_params_t *)boot_params_addr;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     if (boot_params->efi_info.loader_signature == EFI64_LOADER_SIGNATURE) {
         uintptr_t system_table_addr = (uintptr_t)boot_params->efi_info.sys_tab_hi << 32 | boot_params->efi_info.sys_tab;
         if (system_table_addr != 0) {
diff --git a/system/screen.c b/system/screen.c
index 914f17d..b12026a 100644
--- a/system/screen.c
+++ b/system/screen.c
@@ -306,7 +306,7 @@ void screen_init(void)
         }
 
         lfb_base = screen_info->lfb_base;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
         if (LFB_CAPABILITY_64BIT_BASE & screen_info->capabilities) {
             lfb_base |= (uintptr_t)screen_info->ext_lfb_base << 32;
         }
diff --git a/system/smbios.c b/system/smbios.c
index 5b5d5b1..c42813a 100644
--- a/system/smbios.c
+++ b/system/smbios.c
@@ -42,7 +42,7 @@ static char *get_tstruct_string(struct tstruct_header *header, uint16_t maxlen,
     return NULL;
 }
 
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
 static smbiosv2_t *find_smbiosv2_in_efi64_system_table(efi64_system_table_t *system_table)
 {
     efi64_config_table_t *config_tables = (efi64_config_table_t *) map_region(system_table->config_tables, system_table->num_config_tables * sizeof(efi64_config_table_t), true);
@@ -90,7 +90,7 @@ static uintptr_t find_smbiosv2_adr(void)
             }
         }
     }
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     if (rp == NULL && efi_info -> loader_signature == EFI64_LOADER_SIGNATURE) {
         // EFI64
         if (rp == NULL && efi_info->loader_signature == EFI64_LOADER_SIGNATURE) {
diff --git a/system/usbhcd.c b/system/usbhcd.c
index 159b443..9afaf46 100644
--- a/system/usbhcd.c
+++ b/system/usbhcd.c
@@ -424,7 +424,7 @@ static void reset_usb_controller(hci_info_t *hci)
     uintptr_t mmio_size = pci_config_read32(bus, dev, func, bar);
     pci_config_write32(bus, dev, func, bar, base_addr);
     bool in_io_space = base_addr & 0x1;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     if (!in_io_space && (base_addr & 0x4)) {
         base_addr += (uintptr_t)pci_config_read32(bus, dev, func, bar + 4) << 32;
         pci_config_write32(bus, dev, func, bar + 4, 0xffffffff);
diff --git a/tests/own_addr.c b/tests/own_addr.c
index 8462aaf..612c1cd 100644
--- a/tests/own_addr.c
+++ b/tests/own_addr.c
@@ -135,7 +135,7 @@ int test_own_addr2(int my_cpu, int stage)
     // Calculate the offset (in pages) between the virtual address and the physical address.
     offset = (vm_map[0].pm_base_addr / VM_WINDOW_SIZE) * VM_WINDOW_SIZE;
     offset = (offset >= VM_PINNED_SIZE) ? offset - VM_PINNED_SIZE : 0;
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     // Convert to a byte address offset. This will translate the virtual address into a physical address.
     offset *= PAGE_SIZE;
 #else
diff --git a/tests/test_helper.h b/tests/test_helper.h
index 6dba727..f3ecbf3 100644
--- a/tests/test_helper.h
+++ b/tests/test_helper.h
@@ -20,7 +20,7 @@
  * Test word atomic read and write functions.
  */
 #include "memrw.h"
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
 #define read_word   read64
 #define write_word  write64
 #else
@@ -73,7 +73,7 @@ static inline uintptr_t round_up(uintptr_t value, size_t align_size)
 static inline testword_t prsg(testword_t state)
 {
     // This uses the algorithms described at https://en.wikipedia.org/wiki/Xorshift
-#ifdef __x86_64__
+#if (ARCH_BITS == 64)
     state ^= state << 13;
     state ^= state >> 7;
     state ^= state << 17;