diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000000..21f3ce6263
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,4 @@
+fn main() {
+    println!("cargo:rustc-check-cfg=cfg(hyper_unstable_ffi)");
+    println!("cargo:rustc-check-cfg=cfg(hyper_unstable_tracing)");
+}