diff --git a/kernel/build.rs b/kernel/build.rs
index 32ddd191c..0985ab864 100644
--- a/kernel/build.rs
+++ b/kernel/build.rs
@@ -10,10 +10,9 @@ use std::path::PathBuf;
 fn main() {
     let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
     let target = env::var("TARGET").unwrap();
+    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
     let name = env::var("CARGO_PKG_NAME").unwrap();
 
-    let target_os = target.split('-').nth(2).unwrap_or("none");
-
     // If we're not running on a desktop-class operating system, emit the "baremetal"
     // config setting. This will enable software to do tasks such as
     // managing memory.
diff --git a/services/gam/build.rs b/services/gam/build.rs
index 43c3deb4f..2db940193 100644
--- a/services/gam/build.rs
+++ b/services/gam/build.rs
@@ -2,9 +2,7 @@
 use std::env;
 
 fn main() {
-    let target = env::var("TARGET").unwrap();
-
-    let target_os = target.split('-').nth(2).unwrap_or("none");
+    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
 
     // If we're not running on a desktop-class operating system, emit the "baremetal"
     // config setting. This will enable software to do tasks such as
diff --git a/services/kernel-test/build.rs b/services/kernel-test/build.rs
index 43c3deb4f..2db940193 100644
--- a/services/kernel-test/build.rs
+++ b/services/kernel-test/build.rs
@@ -2,9 +2,7 @@
 use std::env;
 
 fn main() {
-    let target = env::var("TARGET").unwrap();
-
-    let target_os = target.split('-').nth(2).unwrap_or("none");
+    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
 
     // If we're not running on a desktop-class operating system, emit the "baremetal"
     // config setting. This will enable software to do tasks such as
diff --git a/xous-rs/build.rs b/xous-rs/build.rs
index 5af5b4b65..5373d5a9c 100644
--- a/xous-rs/build.rs
+++ b/xous-rs/build.rs
@@ -1,3 +1,4 @@
+use core::panic;
 // NOTE: Adapted from cortex-m/build.rs
 use std::env;
 use std::fs;
@@ -6,10 +7,9 @@ use std::path::PathBuf;
 fn main() {
     let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
     let target = env::var("TARGET").unwrap();
+    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
     let name = env::var("CARGO_PKG_NAME").unwrap();
 
-    let target_os = target.split('-').nth(2).unwrap_or("none");
-
     // If we're not running on a desktop-class operating system, emit the "baremetal"
     // config setting. This will enable software to do tasks such as
     // managing memory.