diff --git a/include/utility b/include/utility
index 30e26f163..1dce49df4 100644
--- a/include/utility
+++ b/include/utility
@@ -989,8 +989,10 @@ __murmur2_or_cityhash<_Size, 32>::operator()(const void* __key, _Size __len)
     {
     case 3:
         __h ^= __data[2] << 16;
+        _LIBCPP_FALLTHROUGH();
     case 2:
         __h ^= __data[1] << 8;
+        _LIBCPP_FALLTHROUGH();
     case 1:
         __h ^= __data[0];
         __h *= __m;