diff --git a/include/llvm/IR/ValueMap.h b/include/llvm/IR/ValueMap.h
index 1503aed621d..f196f334b60 100644
--- a/include/llvm/IR/ValueMap.h
+++ b/include/llvm/IR/ValueMap.h
@@ -45,8 +45,10 @@ class ValueMapConstIterator;
 /// This class defines the default behavior for configurable aspects of
 /// ValueMap<>.  User Configs should inherit from this class to be as compatible
 /// as possible with future versions of ValueMap.
-template<typename KeyT>
+template<typename KeyT, typename MutexT = sys::Mutex>
 struct ValueMapConfig {
+  typedef MutexT mutex_type;
+
   /// If FollowRAUW is true, the ValueMap will update mappings on RAUW. If it's
   /// false, the ValueMap will leave the original mapping in place.
   enum { FollowRAUW = true };
@@ -67,7 +69,7 @@ struct ValueMapConfig {
   /// and onDelete) and not inside other ValueMap methods.  NULL means that no
   /// mutex is necessary.
   template<typename ExtraDataT>
-  static sys::Mutex *getMutex(const ExtraDataT &/*Data*/) { return nullptr; }
+  static mutex_type *getMutex(const ExtraDataT &/*Data*/) { return nullptr; }
 };
 
 /// See the file comment.
@@ -212,7 +214,7 @@ public:
   void deleted() override {
     // Make a copy that won't get changed even when *this is destroyed.
     ValueMapCallbackVH Copy(*this);
-    sys::Mutex *M = Config::getMutex(Copy.Map->Data);
+    typename Config::mutex_type *M = Config::getMutex(Copy.Map->Data);
     if (M)
       M->acquire();
     Config::onDelete(Copy.Map->Data, Copy.Unwrap());  // May destroy *this.
@@ -225,7 +227,7 @@ public:
            "Invalid RAUW on key of ValueMap<>");
     // Make a copy that won't get changed even when *this is destroyed.
     ValueMapCallbackVH Copy(*this);
-    sys::Mutex *M = Config::getMutex(Copy.Map->Data);
+    typename Config::mutex_type *M = Config::getMutex(Copy.Map->Data);
     if (M)
       M->acquire();
 
diff --git a/unittests/IR/ValueMapTest.cpp b/unittests/IR/ValueMapTest.cpp
index 3427c913328..d480865805c 100644
--- a/unittests/IR/ValueMapTest.cpp
+++ b/unittests/IR/ValueMapTest.cpp
@@ -177,10 +177,10 @@ TYPED_TEST(ValueMapTest, ConfiguredCollisionBehavior) {
   // TODO: Implement this when someone needs it.
 }
 
-template<typename KeyT>
-struct LockMutex : ValueMapConfig<KeyT> {
+template<typename KeyT, typename MutexT>
+struct LockMutex : ValueMapConfig<KeyT, MutexT> {
   struct ExtraData {
-    sys::Mutex *M;
+    mutex_type *M;
     bool *CalledRAUW;
     bool *CalledDeleted;
   };
@@ -192,15 +192,15 @@ struct LockMutex : ValueMapConfig<KeyT> {
     *Data.CalledDeleted = true;
     EXPECT_FALSE(Data.M->tryacquire()) << "Mutex should already be locked.";
   }
-  static sys::Mutex *getMutex(const ExtraData &Data) { return Data.M; }
+  static mutex_type *getMutex(const ExtraData &Data) { return Data.M; }
 };
 #if LLVM_ENABLE_THREADS
 TYPED_TEST(ValueMapTest, LocksMutex) {
   sys::Mutex M(false);  // Not recursive.
   bool CalledRAUW = false, CalledDeleted = false;
-  typename LockMutex<TypeParam*>::ExtraData Data =
-    {&M, &CalledRAUW, &CalledDeleted};
-  ValueMap<TypeParam*, int, LockMutex<TypeParam*> > VM(Data);
+  typedef LockMutex<TypeParam*, sys::Mutex> ConfigType;
+  typename ConfigType::ExtraData Data = {&M, &CalledRAUW, &CalledDeleted};
+  ValueMap<TypeParam*, int, ConfigType> VM(Data);
   VM[this->BitcastV.get()] = 7;
   this->BitcastV->replaceAllUsesWith(this->AddV.get());
   this->AddV.reset();