diff --git a/src/librustc/arena.rs b/src/librustc/arena.rs
index 51588953a2f..d2797e65240 100644
--- a/src/librustc/arena.rs
+++ b/src/librustc/arena.rs
@@ -139,7 +139,7 @@ pub trait ArenaAllocatable {}
 
 impl<T: Copy> ArenaAllocatable for T {}
 
-pub unsafe trait ArenaField<'tcx>: Sized {
+unsafe trait ArenaField<'tcx>: Sized {
     /// Returns a specific arena to allocate from.
     /// If None is returned, the DropArena will be used.
     fn arena<'a>(arena: &'a Arena<'tcx>) -> Option<&'a TypedArena<Self>>;