diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index 46d35514..501478db 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -366,7 +366,7 @@ int HttpDownstreamConnection::push_request_headers() {
   // Assume that method and request path do not contain \r\n.
   auto meth = http2::to_method_string(req.method);
   buf->append(meth);
-  buf->append(" ");
+  buf->append(' ');
 
   if (connect_method) {
     buf->append(authority);
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index 25e23603..067c2d43 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -1013,7 +1013,7 @@ int HttpsUpstream::on_downstream_header_complete(Downstream *downstream) {
   buf->append(util::utos(req.http_major));
   buf->append(".");
   buf->append(util::utos(req.http_minor));
-  buf->append(" ");
+  buf->append(' ');
   buf->append(http2::stringify_status(balloc, resp.http_status));
   buf->append(' ');
   buf->append(http2::get_reason_phrase(resp.http_status));