diff --git a/include/rapidjson/internal/biginteger.h b/include/rapidjson/internal/biginteger.h
index 3e97920..5719a2a 100755
--- a/include/rapidjson/internal/biginteger.h
+++ b/include/rapidjson/internal/biginteger.h
@@ -252,7 +252,8 @@ private:
             (*outHigh)++;
         return low;
 #elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) && defined(__x86_64__)
-        unsigned __int128 p = static_cast<unsigned __int128>(a) * static_cast<unsigned __int128>(b);
+        __extension__ typedef unsigned __int128 uint128;
+        uint128 p = static_cast<uint128>(a) * static_cast<uint128>(b);
         p += k;
         *outHigh = p >> 64;
         return static_cast<uint64_t>(p);
diff --git a/include/rapidjson/internal/diyfp.h b/include/rapidjson/internal/diyfp.h
index 174b9fa..1b36f66 100644
--- a/include/rapidjson/internal/diyfp.h
+++ b/include/rapidjson/internal/diyfp.h
@@ -75,7 +75,8 @@ struct DiyFp {
             h++;
         return DiyFp(h, e + rhs.e + 64);
 #elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) && defined(__x86_64__)
-        unsigned __int128 p = static_cast<unsigned __int128>(f) * static_cast<unsigned __int128>(rhs.f);
+        __extension__ typedef unsigned __int128 uint128;
+        uint128 p = static_cast<uint128>(f) * static_cast<uint128>(rhs.f);
         uint64_t h = p >> 64;
         uint64_t l = static_cast<uint64_t>(p);
         if (l & (uint64_t(1) << 63)) // rounding