diff --git a/include/llvm/IR/Metadata.h b/include/llvm/IR/Metadata.h
index 7f8dca68bfa..6f38013b877 100644
--- a/include/llvm/IR/Metadata.h
+++ b/include/llvm/IR/Metadata.h
@@ -45,7 +45,7 @@ protected:
 
 public:
   static bool classof(const Value *V) {
-    return V->getValueID() == MDNodeVal;
+    return V->getValueID() == MDNodeVal || V->getValueID() == MDStringVal;
   }
 };
 
@@ -54,15 +54,14 @@ public:
 ///
 /// These are used to efficiently contain a byte sequence for metadata.
 /// MDString is always unnamed.
-///
-/// TODO: Inherit from Metadata.
-class MDString : public Value {
+class MDString : public Metadata {
   friend class StringMapEntry<MDString>;
 
   virtual void anchor();
   MDString(const MDString &) LLVM_DELETED_FUNCTION;
 
-  explicit MDString(LLVMContext &C);
+  explicit MDString(LLVMContext &Context)
+      : Metadata(Context, Value::MDStringVal) {}
 
   /// \brief Shadow Value::getName() to prevent its use.
   StringRef getName() const LLVM_DELETED_FUNCTION;
diff --git a/lib/IR/Metadata.cpp b/lib/IR/Metadata.cpp
index 0f5f969d2f6..cdd106033f8 100644
--- a/lib/IR/Metadata.cpp
+++ b/lib/IR/Metadata.cpp
@@ -37,9 +37,6 @@ Metadata::Metadata(LLVMContext &Context, unsigned ID)
 
 void MDString::anchor() { }
 
-MDString::MDString(LLVMContext &C)
-  : Value(Type::getMetadataTy(C), Value::MDStringVal) {}
-
 MDString *MDString::get(LLVMContext &Context, StringRef Str) {
   auto &Store = Context.pImpl->MDStringCache;
   auto I = Store.find(Str);