diff --git a/build.rs b/build.rs
index fa809bf..b342e2a 100644
--- a/build.rs
+++ b/build.rs
@@ -1,3 +1,3 @@
 fn main() {
-    built::write_built_file().unwrap();
+    built::write_built_file().expect("appropriate environment variables should have been set");
 }