diff --git a/crates/oxc_transformer/src/es2015/function_name.rs b/crates/oxc_transformer/src/es2015/function_name.rs
index 635ef35d1..bf779b200 100644
--- a/crates/oxc_transformer/src/es2015/function_name.rs
+++ b/crates/oxc_transformer/src/es2015/function_name.rs
@@ -162,7 +162,7 @@ fn create_valid_identifier(
     // }
 
     let id = Atom::from(
-        atom.chars().map(|c| if is_identifier_part(c) { c } else { '-' }).collect::<String>(),
+        atom.chars().map(|c| if is_identifier_part(c) { c } else { '_' }).collect::<String>(),
     );
 
     let id = if id == "" {