diff --git a/include/llvm/ADT/ImmutableMap.h b/include/llvm/ADT/ImmutableMap.h
index ae2a335942d..bbf34c566d8 100644
--- a/include/llvm/ADT/ImmutableMap.h
+++ b/include/llvm/ADT/ImmutableMap.h
@@ -76,7 +76,8 @@ public:
   /// should use a Factory object to create maps instead of directly
   /// invoking the constructor, but there are cases where make this
   /// constructor public is useful.
-  explicit ImmutableMap(TreeTy* R) : Root(R) {}
+  explicit ImmutableMap(TreeTy* R) : Root(R) {}  
+  explicit ImmutableMap(const TreeTy* R) : Root(const_cast<TreeTy*>(R)) {}
   
   class Factory {
     typename TreeTy::Factory F;