diff --git a/include/gtest/internal/gtest-port.h b/include/gtest/internal/gtest-port.h
index cb870c9e..04938929 100644
--- a/include/gtest/internal/gtest-port.h
+++ b/include/gtest/internal/gtest-port.h
@@ -1416,6 +1416,8 @@ class ThreadLocal {
 class Mutex {
  public:
   Mutex() {}
+  void Lock() {}
+  void Unlock() {}
   void AssertHeld() const {}
 };