diff --git a/googletest/include/gtest/internal/gtest-port.h b/googletest/include/gtest/internal/gtest-port.h
index 4cd74fb6..8d1b6191 100644
--- a/googletest/include/gtest/internal/gtest-port.h
+++ b/googletest/include/gtest/internal/gtest-port.h
@@ -785,13 +785,17 @@ typedef struct _RTL_CRITICAL_SECTION GTEST_CRITICAL_SECTION;
 #  define GTEST_HAS_SEH 0
 # endif
 
-#define GTEST_IS_THREADSAFE \
-    (GTEST_HAS_MUTEX_AND_THREAD_LOCAL_ \
-     || (GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT) \
-     || GTEST_HAS_PTHREAD)
-
 #endif  // GTEST_HAS_SEH
 
+#ifndef GTEST_IS_THREADSAFE
+
+# define GTEST_IS_THREADSAFE \
+    ( GTEST_HAS_MUTEX_AND_THREAD_LOCAL_ \
+      || (GTEST_OS_WINDOWS && !GTEST_OS_WINDOWS_PHONE && !GTEST_OS_WINDOWS_RT) \
+      || GTEST_HAS_PTHREAD)
+
+#endif // GTEST_IS_THREADSAFE
+
 // GTEST_API_ qualifies all symbols that must be exported. The definitions below
 // are guarded by #ifndef to give embedders a chance to define GTEST_API_ in
 // gtest/internal/custom/gtest-port.h