diff --git a/src/pipeline.cc b/src/pipeline.cc
index 054584ac..347ecab7 100644
--- a/src/pipeline.cc
+++ b/src/pipeline.cc
@@ -424,8 +424,8 @@ void LaunchStdin() {
   std::thread([]() {
     set_thread_name("stdin");
     std::string str;
+    const std::string_view kContentLength("Content-Length: ");
     while (true) {
-      constexpr std::string_view kContentLength("Content-Length: ");
       int len = 0;
       str.clear();
       while (true) {