Index: llvm/trunk/include/llvm/ADT/DenseSet.h
===================================================================
--- llvm/trunk/include/llvm/ADT/DenseSet.h
+++ llvm/trunk/include/llvm/ADT/DenseSet.h
@@ -136,8 +136,8 @@
   public:
     using difference_type = typename MapTy::const_iterator::difference_type;
     using value_type = ValueT;
-    using pointer = value_type *;
-    using reference = value_type &;
+    using pointer = const value_type *;
+    using reference = const value_type &;
     using iterator_category = std::forward_iterator_tag;
 
     ConstIterator() = default;
Index: llvm/trunk/unittests/ADT/DenseSetTest.cpp
===================================================================
--- llvm/trunk/unittests/ADT/DenseSetTest.cpp
+++ llvm/trunk/unittests/ADT/DenseSetTest.cpp
@@ -15,6 +15,13 @@
 
 namespace {
 
+static_assert(std::is_const<std::remove_pointer<
+                  DenseSet<int>::const_iterator::pointer>::type>::value,
+              "Iterator pointer type should be const");
+static_assert(std::is_const<std::remove_reference<
+                  DenseSet<int>::const_iterator::reference>::type>::value,
+              "Iterator reference type should be const");
+
 // Test hashing with a set of only two entries.
 TEST(DenseSetTest, DoubleEntrySetTest) {
   llvm::DenseSet<unsigned> set(2);