diff --git a/src/librustc_span/source_map.rs b/src/librustc_span/source_map.rs
index 51f554176630..dc85f7990b92 100644
--- a/src/librustc_span/source_map.rs
+++ b/src/librustc_span/source_map.rs
@@ -95,7 +95,7 @@ impl StableSourceFileId {
         )
     }
 
-    pub fn new_from_pieces(
+    fn new_from_pieces(
         name: &FileName,
         name_was_remapped: bool,
         unmapped_path: Option<&FileName>,