diff --git a/metricsd/uploader/sender_http.cc b/metricsd/uploader/sender_http.cc
index 4b572a6..1f775df 100644
--- a/metricsd/uploader/sender_http.cc
+++ b/metricsd/uploader/sender_http.cc
@@ -23,7 +23,7 @@
 #include <brillo/http/http_utils.h>
 #include <brillo/mime_utils.h>
 
-HttpSender::HttpSender(const std::string server_url)
+HttpSender::HttpSender(const std::string& server_url)
     : server_url_(server_url) {}
 
 bool HttpSender::Send(const std::string& content,
diff --git a/metricsd/uploader/sender_http.h b/metricsd/uploader/sender_http.h
index 4f1c08f..0d64c74 100644
--- a/metricsd/uploader/sender_http.h
+++ b/metricsd/uploader/sender_http.h
@@ -26,7 +26,7 @@
 // Sender implemented using http_utils from libbrillo
 class HttpSender : public Sender {
  public:
-  explicit HttpSender(std::string server_url);
+  explicit HttpSender(const std::string& server_url);
   ~HttpSender() override = default;
   // Sends |content| whose SHA1 hash is |hash| to server_url with a synchronous
   // POST request to server_url.