diff --git a/parallel_hashmap/phmap.h b/parallel_hashmap/phmap.h
index 748c003..badde58 100644
--- a/parallel_hashmap/phmap.h
+++ b/parallel_hashmap/phmap.h
@@ -289,7 +289,7 @@ inline __m128i _mm_cmpgt_epi8_fixed(__m128i a, __m128i b) {
   #pragma GCC diagnostic ignored "-Woverflow"
 
   if (std::is_unsigned<char>::value) {
-    const __m128i mask = _mm_set1_epi8(0x80);
+    const __m128i mask = _mm_set1_epi8(static_cast<char>(0x80));
     const __m128i diff = _mm_subs_epi8(b, a);
     return _mm_cmpeq_epi8(_mm_and_si128(diff, mask), mask);
   }
diff --git a/parallel_hashmap/phmap_bits.h b/parallel_hashmap/phmap_bits.h
index c48e8ea..7eb3fac 100644
--- a/parallel_hashmap/phmap_bits.h
+++ b/parallel_hashmap/phmap_bits.h
@@ -339,7 +339,8 @@ PHMAP_BASE_INTERNAL_FORCEINLINE int CountTrailingZerosNonZero32(uint32_t n) {
 #ifdef PHMAP_HAVE_INTRINSIC_INT128
     inline uint64_t umul128(uint64_t a, uint64_t b, uint64_t* high) 
     {
-        auto result = static_cast<unsigned __int128>(a) * static_cast<unsigned __int128>(b);
+        auto result = static_cast<__extension__ unsigned __int128>(a) * 
+                      static_cast<__extension__ unsigned __int128>(b);
         *high = static_cast<uint64_t>(result >> 64);
         return static_cast<uint64_t>(result);
     }