--- a/tools/db_bench_tool.cc
+++ b/tools/db_bench_tool.cc
@@ -6442,7 +6442,7 @@
       // Pick a Iterator to use
       size_t db_idx_to_use =
           (db_.db == nullptr)
-              ? (size_t{thread->rand.Next()} % multi_dbs_.size())
+              ? (size_t{static_cast<size_t>(thread->rand.Next())} % multi_dbs_.size())
               : 0;
       std::unique_ptr<Iterator> single_iter;
       Iterator* iter_to_use;
