diff --git a/examples/server/utils.hpp b/examples/server/utils.hpp
index 3429f0b43..f27af81e9 100644
--- a/examples/server/utils.hpp
+++ b/examples/server/utils.hpp
@@ -378,7 +378,7 @@ static json oaicompat_completion_params_parse(
     return llama_params;
 }
 
-static json format_final_response_oaicompat(const json & request, json result, std::string completion_id, bool streaming = false) {
+static json format_final_response_oaicompat(const json & request, json result, const std::string & completion_id, bool streaming = false) {
     bool stopped_word        = result.count("stopped_word") != 0;
     bool stopped_eos         = json_value(result, "stopped_eos", false);
     int num_tokens_predicted = json_value(result, "tokens_predicted", 0);