1 files changed, 2 insertions, 1 deletions
diff --git a/src/libstd/map.rs b/src/libstd/map.rs
index 765d40339d3..9f78f98fa31 100644
--- a/src/libstd/map.rs
+++ b/src/libstd/map.rs
@@ -341,7 +341,8 @@ pub mod chained {
             wr.write_str(~" }");
         }
 
-        fn to_str() -> ~str {
+        pure fn to_str() -> ~str unsafe {
+            // Meh -- this should be safe
             do io::with_str_writer |wr| { self.to_writer(wr) }
         }
     }