diff --git a/base/set.jl b/base/set.jl
index fb837fbf86166..d6d8086c13c44 100644
--- a/base/set.jl
+++ b/base/set.jl
@@ -17,6 +17,8 @@ Set() = Set{Any}()
 Construct a [`Set`](@ref) of the values generated by the given iterable object, or an
 empty set. Should be used instead of [`BitSet`](@ref) for sparse integer sets, or
 for sets of arbitrary objects.
+!!! note
+    Iteration over `Set` is unordered.
 """
 Set(itr) = _Set(itr, IteratorEltype(itr))