diff --git a/third_party/lang-items/src/panic_handler.rs b/third_party/lang-items/src/panic_handler.rs
new file mode 100644
index 0000000..c63a9c1
--- /dev/null
+++ b/third_party/lang-items/src/panic_handler.rs
@@ -0,0 +1,72 @@
+//! Lang item required to make the normal `main` work in applications
+//!
+//! This is how the `start` lang item works:
+//! When `rustc` compiles a binary crate, it creates a `main` function that looks
+//! like this:
+//!
+//! ```
+//! #[export_name = "main"]
+//! pub extern "C" fn rustc_main(argc: isize, argv: *const *const u8) -> isize {
+//!     start(main, argc, argv)
+//! }
+//! ```
+//!
+//! Where `start` is this function and `main` is the binary crate's `main`
+//! function.
+//!
+//! The final piece is that the entry point of our program, _start, has to call
+//! `rustc_main`. That's covered by the `_start` function in the root of this
+//! crate.
+
+use crate::led;
+use crate::timer;
+use crate::timer::Duration;
+use core::alloc::Layout;
+use core::panic::PanicInfo;
+
+#[lang = "start"]
+extern "C" fn start<T>(main: fn() -> T, _argc: isize, _argv: *const *const u8) -> i32
+where
+    T: Termination,
+{
+    main().report()
+}
+
+pub trait Termination {
+    fn report(self) -> i32;
+}
+
+impl Termination for () {
+    fn report(self) -> i32 {
+        0
+    }
+}
+
+#[panic_handler]
+fn panic_handler(_info: &PanicInfo) -> ! {
+    // Signal a panic using the LowLevelDebug capsule (if available).
+    super::debug::low_level_status_code(1);
+
+    // Flash all LEDs (if available).
+    loop {
+        for led in led::all() {
+            led.on();
+        }
+        timer::sleep(Duration::from_ms(100));
+        for led in led::all() {
+            led.off();
+        }
+        timer::sleep(Duration::from_ms(100));
+    }
+}
+
+#[alloc_error_handler]
+fn cycle_leds(_: Layout) -> ! {
+    loop {
+        for led in led::all() {
+            led.on();
+            timer::sleep(Duration::from_ms(100));
+            led.off();
+        }
+    }
+}