diff --git a/src/helpers.rs b/src/helpers.rs
index 604151d6..3aabb8e5 100644
--- a/src/helpers.rs
+++ b/src/helpers.rs
@@ -22,7 +22,7 @@ pub fn get_map<S: StreamChunks>(
   stream: &S,
   options: &MapOptions,
 ) -> Option<SourceMap> {
-  let mut mappings = Vec::with_capacity(stream.mappings_size_hint());
+  let mut mappings = Vec::new();
   let mut sources: Vec<Cow<'static, str>> = Vec::new();
   let mut sources_content: Vec<Cow<'static, str>> = Vec::new();
   let mut names: Vec<Cow<'static, str>> = Vec::new();