diff --git a/src/main.rs b/src/main.rs
index 4381bad..5fac746 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -8,7 +8,7 @@ use google_rest_api_generator::generate;
 fn main() -> Result<(), Box<dyn Error>> {
     let args: Vec<_> = std::env::args().skip(1).collect();
     if args.len() != 2 {
-        eprintln!("Usage: main discovery.json output_directory");
+        return Err("Usage: main discovery.json output_directory".into());
     }
     let mut file = File::open(&args[0])?;
     let mut contents = String::new();