diff --git a/crates/macro/src/expand/napi.rs b/crates/macro/src/expand/napi.rs
index 608321bc..5e15c553 100644
--- a/crates/macro/src/expand/napi.rs
+++ b/crates/macro/src/expand/napi.rs
@@ -130,7 +130,8 @@ fn output_wasi_register_def(napi: &Napi) {
         let mut writer = BufWriter::<fs::File>::new(file);
         let pkg_name: String = std::env::var("CARGO_PKG_NAME").expect("CARGO_PKG_NAME is not set");
         writer.write_all(format!("{pkg_name}: {}", napi.register_name()).as_bytes())?;
-        writer.write_all("\n".as_bytes())
+        writer.write_all("\n".as_bytes())?;
+        writer.flush()
       })
       .unwrap_or_else(|e| {
         println!("Failed to write wasi register file: {:?}", e);