diff --git a/src/shrpx_http2_downstream_connection.cc b/src/shrpx_http2_downstream_connection.cc
index 8d89e48d..ab5c20d2 100644
--- a/src/shrpx_http2_downstream_connection.cc
+++ b/src/shrpx_http2_downstream_connection.cc
@@ -426,11 +426,10 @@ int Http2DownstreamConnection::push_request_headers() {
     DCLOG(INFO, this) << "HTTP request headers\n" << ss.str();
   }
 
-  auto content_length = req.fs.header(http2::HD_CONTENT_LENGTH);
-  // TODO check content-length: 0 case
-
-  if (req.method == HTTP_CONNECT || chunked_encoding || content_length ||
-      req.http2_expect_body) {
+  // Add body as long as transfer-encoding is given even if
+  // req.fs.content_length == 0 to forward trailer fields.
+  if (req.method == HTTP_CONNECT || transfer_encoding ||
+      req.fs.content_length > 0 || req.http2_expect_body) {
     // Request-body is expected.
     nghttp2_data_provider data_prd{{}, http2_data_read_callback};
     rv = http2session_->submit_request(this, nva.data(), nva.size(), &data_prd);
diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index b6337c7b..d2251789 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -373,9 +373,9 @@ int HttpDownstreamConnection::push_request_headers() {
     buf->append("\r\n");
   }
 
-  if (!connect_method && req.http2_expect_body &&
-      !req.fs.header(http2::HD_CONTENT_LENGTH)) {
-
+  // set transfer-encoding only when content-length is unknown and
+  // request body is expected.
+  if (!connect_method && req.http2_expect_body && req.fs.content_length == -1) {
     downstream_->set_chunked_request(true);
     buf->append("Transfer-Encoding: chunked\r\n");
   }
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index 86195019..1dff8cd6 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -312,8 +312,10 @@ int htp_hdrs_completecb(http_parser *htp) {
     ULOG(INFO, upstream) << "HTTP request headers\n" << ss.str();
   }
 
-  if (req.fs.parse_content_length() != 0) {
-    return -1;
+  // set content-length if no transfer-encoding is given.  If
+  // transfer-encoding is given, leave req.fs.content_length to -1.
+  if (!req.fs.header(http2::HD_TRANSFER_ENCODING)) {
+    req.fs.content_length = htp->content_length;
   }
 
   auto host = req.fs.header(http2::HD_HOST);