diff --git a/db/db_impl.cc b/db/db_impl.cc
index ba8d9ff53..76fec5ef6 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -123,7 +123,8 @@ Options SanitizeOptions(const std::string& dbname,
   result.comparator = icmp;
   result.filter_policy = (src.filter_policy != nullptr) ? ipolicy : nullptr;
   ClipToRange(&result.max_open_files,            20,     1000000);
-  ClipToRange(&result.write_buffer_size,         64<<10, 1<<30);
+  ClipToRange(&result.write_buffer_size,         ((size_t)64)<<10,
+                                                 ((size_t)64)<<30);
   ClipToRange(&result.block_size,                1<<10,  4<<20);
   if (result.info_log == nullptr) {
     Status s = CreateLoggerFromOptions(dbname, result.db_log_dir, src.env,