diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 004bbd3a..afc9e2ef 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -1805,7 +1805,7 @@ void worker_acceptcb(struct ev_loop *loop, ev_async *w, int revents) {
     q.swap(worker->q);
   }
 
-  for (auto c : q) {
+  for (const auto &c : q) {
     sessions->accept_connection(c.fd);
   }
 }
diff --git a/src/shrpx.cc b/src/shrpx.cc
index 4b9eb58e..b586dc13 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -1093,7 +1093,7 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
     auto portenv = getenv(ENV_PORT.c_str());
     if (portenv) {
       size_t i = 1;
-      for (auto env_name : {ENV_LISTENER4_FD, ENV_LISTENER6_FD}) {
+      for (const auto &env_name : {ENV_LISTENER4_FD, ENV_LISTENER6_FD}) {
         auto fdenv = getenv(env_name.c_str());
         if (fdenv) {
           auto name = ENV_ACCEPT_PREFIX.str();