diff --git a/llvm/include/llvm/ADT/DepthFirstIterator.h b/llvm/include/llvm/ADT/DepthFirstIterator.h
--- a/llvm/include/llvm/ADT/DepthFirstIterator.h
+++ b/llvm/include/llvm/ADT/DepthFirstIterator.h
@@ -164,6 +164,7 @@
   bool operator!=(const df_iterator &x) const { return !(*this == x); }
 
   const NodeRef &operator*() const { return VisitStack.back().first; }
+  NodeRef &operator*() { return VisitStack.back().first; }
 
   // This is a nonstandard operator-> that dereferences the pointer an extra
   // time... so that you can actually call methods ON the Node, because
diff --git a/llvm/include/llvm/ADT/iterator.h b/llvm/include/llvm/ADT/iterator.h
--- a/llvm/include/llvm/ADT/iterator.h
+++ b/llvm/include/llvm/ADT/iterator.h
@@ -268,7 +268,8 @@
     return I < RHS.I;
   }
 
-  ReferenceT operator*() const { return *I; }
+  const ReferenceT operator*() const { return *I; }
+  ReferenceT operator*() { return *I; }
 };
 
 /// An iterator type that allows iterating over the pointees via some