diff --git a/src/comp/syntax/ext/expand.rs b/src/comp/syntax/ext/expand.rs
index 09748a3168e..8b20bba9ce1 100644
--- a/src/comp/syntax/ext/expand.rs
+++ b/src/comp/syntax/ext/expand.rs
@@ -70,7 +70,7 @@ fn expand_crate(sess: session::session, c: @crate) -> @crate {
         {fold_expr: bind expand_expr(exts, cx, _, _, afp.fold_expr)
             with *afp};
     let f = make_fold(f_pre);
-    let cm = parse_expr_from_source_str("-", core_macros(),
+    let cm = parse_expr_from_source_str("<anon>", core_macros(),
                                         sess.opts.cfg,
                                         sess.parse_sess);