diff --git a/agb/src/lib.rs b/agb/src/lib.rs
index 57cb1b64..28bfc684 100644
--- a/agb/src/lib.rs
+++ b/agb/src/lib.rs
@@ -12,6 +12,7 @@
 )]
 #![feature(alloc_error_handler)]
 #![feature(allocator_api)]
+#![feature(asm_const)]
 #![warn(clippy::all)]
 #![deny(clippy::must_use_candidate)]
 #![deny(clippy::trivially_copy_pass_by_ref)]
diff --git a/agb/src/syscall.rs b/agb/src/syscall.rs
index cf28c71a..69ff353f 100644
--- a/agb/src/syscall.rs
+++ b/agb/src/syscall.rs
@@ -4,10 +4,19 @@ use core::arch::asm;
 
 #[allow(non_snake_case)]
 
+const fn swi_map(thumb_id: u32) -> u32 {
+    if cfg!(target_feature="thumb-mode") {
+        thumb_id
+    } else {
+        thumb_id << 16
+    }
+}
+
 pub fn halt() {
     unsafe {
         asm!(
-            "swi 0x02",
+            "swi {SWI}",
+            SWI = const { swi_map(0x02) },
             lateout("r0") _,
             lateout("r1") _,
             lateout("r2") _,
@@ -19,7 +28,8 @@ pub fn halt() {
 pub fn stop() {
     unsafe {
         asm!(
-            "swi 0x03",
+            "swi {SWI}",
+            SWI = const { swi_map(0x03) },
             lateout("r0") _,
             lateout("r1") _,
             lateout("r2") _,
@@ -31,7 +41,8 @@ pub fn stop() {
 pub fn wait_for_interrupt() {
     unsafe {
         asm!(
-            "swi 0x04",
+            "swi {SWI}",
+            SWI = const { swi_map(0x04) },
             lateout("r0") _,
             lateout("r1") _,
             lateout("r2") _,
@@ -45,7 +56,8 @@ pub fn wait_for_interrupt() {
 pub fn wait_for_vblank() {
     unsafe {
         asm!(
-            "swi 0x05",
+            "swi {SWI}",
+            SWI = const { swi_map(0x05) },
             lateout("r0") _,
             lateout("r1") _,
             lateout("r2") _,
@@ -61,7 +73,8 @@ pub fn div(numerator: i32, denominator: i32) -> (i32, i32, i32) {
     let abs_divide: i32;
     unsafe {
         asm!(
-            "swi 0x06",
+            "swi {SWI}",
+            SWI = const { swi_map(0x06) },
             in("r0") numerator,
             in("r1") denominator,
             lateout("r0") divide,
@@ -77,7 +90,8 @@ pub fn sqrt(n: i32) -> i32 {
     let result: i32;
     unsafe {
         asm!(
-            "swi 0x08",
+            "swi {SWI}",
+            SWI = const { swi_map(0x08) },
             in("r0") n,
             lateout("r0") result,
             lateout("r1") _,
@@ -93,7 +107,8 @@ pub fn arc_tan(n: i16) -> i16 {
     let result: i16;
     unsafe {
         asm!(
-            "swi 0x09",
+            "swi {SWI}",
+            SWI = const { swi_map(0x09) },
             in("r0") n,
             lateout("r0") result,
             lateout("r1") _,
@@ -109,7 +124,8 @@ pub fn arc_tan2(x: i16, y: i32) -> i16 {
     let result: i16;
     unsafe {
         asm!(
-            "swi 0x09",
+            "swi {SWI}",
+            SWI = const { swi_map(0x09) },
             in("r0") x,
             in("r1") y,
             lateout("r0") result,