--- a/libcxx/include/thread
+++ b/libcxx/include/thread
@@ -435,7 +435,12 @@ sleep_for(const chrono::duration<_Rep, _Period>& __d)
     using namespace chrono;
     if (__d > duration<_Rep, _Period>::zero())
     {
+#if ! (defined(_LIBCPP_COMPILER_GCC) && (__powerpc__ || __POWERPC__))
+    //  GCC's long double const folding is incomplete for IBM128 long doubles.
         _LIBCPP_CONSTEXPR duration<long double> _Max = nanoseconds::max();
+#else
+        _LIBCPP_CONSTEXPR duration<long double> _Max = duration<long double>(ULLONG_MAX/1000000000ULL) ;
+#endif
         nanoseconds __ns;
         if (__d < _Max)
         {