diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index 11ec9756..9cfc2cc7 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -367,7 +367,7 @@ void append_last_header_value(bool &key_prev, size_t &sum, Headers &headers,
 }
 } // namespace
 
-int FieldStore::index_headers() {
+int FieldStore::parse_content_length() {
   content_length = -1;
 
   for (auto &kv : headers_) {
diff --git a/src/shrpx_downstream.h b/src/shrpx_downstream.h
index 8a855b1c..4306940d 100644
--- a/src/shrpx_downstream.h
+++ b/src/shrpx_downstream.h
@@ -89,10 +89,9 @@ public:
 
   bool header_key_prev() const { return header_key_prev_; }
 
-  // Lower the header field names and indexes header fields.  If there
-  // is any invalid headers (e.g., multiple Content-Length having
-  // different values), returns -1.
-  int index_headers();
+  // Parses content-length, and records it in the field.  If there are
+  // multiple Content-Length, returns -1.
+  int parse_content_length();
 
   // Empties headers.
   void clear_headers();
diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index c5b3da09..9e55f39b 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -572,7 +572,7 @@ int htp_hdrs_completecb(http_parser *htp) {
   resp.http_major = htp->http_major;
   resp.http_minor = htp->http_minor;
 
-  if (resp.fs.index_headers() != 0) {
+  if (resp.fs.parse_content_length() != 0) {
     downstream->set_response_state(Downstream::MSG_BAD_HEADER);
     return -1;
   }
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index c84af459..9eaa5202 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -270,7 +270,7 @@ int htp_hdrs_completecb(http_parser *htp) {
     ULOG(INFO, upstream) << "HTTP request headers\n" << ss.str();
   }
 
-  if (req.fs.index_headers() != 0) {
+  if (req.fs.parse_content_length() != 0) {
     return -1;
   }
 
diff --git a/src/shrpx_spdy_upstream.cc b/src/shrpx_spdy_upstream.cc
index dc4a5db1..d9c22209 100644
--- a/src/shrpx_spdy_upstream.cc
+++ b/src/shrpx_spdy_upstream.cc
@@ -194,7 +194,7 @@ void on_ctrl_recv_callback(spdylay_session *session, spdylay_frame_type type,
       req.fs.add_header_token(name, value, false, token);
     }
 
-    if (req.fs.index_headers() != 0) {
+    if (req.fs.parse_content_length() != 0) {
       if (upstream->error_reply(downstream, 400) != 0) {
         ULOG(FATAL, upstream) << "error_reply failed";
       }