diff --git a/crates/oxc_sourcemap/src/concat_sourcemap_builder.rs b/crates/oxc_sourcemap/src/concat_sourcemap_builder.rs
index eebe77edd..83820776a 100644
--- a/crates/oxc_sourcemap/src/concat_sourcemap_builder.rs
+++ b/crates/oxc_sourcemap/src/concat_sourcemap_builder.rs
@@ -114,7 +114,7 @@ impl ConcatSourceMapBuilder {
             // than cloning an `Arc`.
             self.source_contents.extend(source_contents.iter().map(Arc::clone));
         } else {
-            self.source_contents.extend((0..sourcemap.sources.len()).map(|_| Arc::default()));
+            self.source_contents.extend((0..sourcemap.sources.len()).map(|_| "".into()));
         }
 
         // Extend `names`.