diff --git a/lib/cpp/src/concurrency/Mutex.h b/lib/cpp/src/concurrency/Mutex.h
index f7ee9f2..a33b995 100644
--- a/lib/cpp/src/concurrency/Mutex.h
+++ b/lib/cpp/src/concurrency/Mutex.h
@@ -86,15 +86,34 @@
   const Mutex& mutex_;
 };
 
+
+// Can be used as second argument to RWGuard to make code more readable
+// as to whether we're doing acquireRead() or acquireWrite().
+enum RWGuardType {
+  RW_READ = 0,
+  RW_WRITE = 1,
+};
+
+
 class RWGuard {
   public:
-    RWGuard(const ReadWriteMutex& value, bool write = 0) : rw_mutex_(value) {
+    RWGuard(const ReadWriteMutex& value, bool write = false)
+         : rw_mutex_(value) {
       if (write) {
         rw_mutex_.acquireWrite();
       } else {
         rw_mutex_.acquireRead();
       }
     }
+
+    RWGuard(const ReadWriteMutex& value, RWGuardType type)
+         : rw_mutex_(value) {
+      if (type == RW_WRITE) {
+        rw_mutex_.acquireWrite();
+      } else {
+        rw_mutex_.acquireRead();
+      }
+    }
     ~RWGuard() {
       rw_mutex_.release();
     }