diff --git a/src/libstd/thread/mod.rs b/src/libstd/thread/mod.rs
index a55b32c08a303..eb8e0c1c8ac66 100644
--- a/src/libstd/thread/mod.rs
+++ b/src/libstd/thread/mod.rs
@@ -607,7 +607,7 @@ impl Builder {
 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
     F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
 {
-    Builder::new().spawn(f).unwrap()
+    Builder::new().spawn(f).expect("failed to spawn thread")
 }
 
 /// Gets a handle to the thread that invokes it.