diff --git a/src/http2.cc b/src/http2.cc
index 38d74a3e..04dfb7ad 100644
--- a/src/http2.cc
+++ b/src/http2.cc
@@ -477,6 +477,11 @@ void dump_nv(FILE *out, const HeaderRefs &nva) {
   fflush(out);
 }
 
+void erase_header(HeaderRef *hd) {
+  hd->name = StringRef{};
+  hd->token = -1;
+}
+
 StringRef rewrite_location_uri(BlockAllocator &balloc, const StringRef &uri,
                                const http_parser_url &u,
                                const StringRef &match_host,
diff --git a/src/http2.h b/src/http2.h
index 5ebe11f1..9859930b 100644
--- a/src/http2.h
+++ b/src/http2.h
@@ -227,6 +227,9 @@ void dump_nv(FILE *out, const Headers &nva);
 
 void dump_nv(FILE *out, const HeaderRefs &nva);
 
+// Ereases header in |hd|.
+void erase_header(HeaderRef *hd);
+
 // Rewrites redirection URI which usually appears in location header
 // field. The |uri| is the URI in the location header field. The |u|
 // stores the result of parsed |uri|. The |request_authority| is the
diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index 2519d109..16435a84 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -720,15 +720,33 @@ int htp_hdrs_completecb(http_parser *htp) {
   // 204.  Also server MUST NOT send Transfer-Encoding with a status
   // code 200 to a CONNECT request.  Same holds true with
   // Content-Length.
-  if (resp.http_status == 204 || resp.http_status / 100 == 1 ||
-      (resp.http_status == 200 && req.method == HTTP_CONNECT)) {
+  if (resp.http_status == 204) {
+    if (resp.fs.header(http2::HD_TRANSFER_ENCODING)) {
+      return -1;
+    }
+    // Some server send content-length: 0 for 204.  Until they get
+    // fixed, we accept, but ignore it.
+
+    // Calling parse_content_length() detects duplicated
+    // content-length header fields.
+    if (resp.fs.parse_content_length() != 0) {
+      return -1;
+    }
+    if (resp.fs.content_length != 0) {
+      return -1;
+    }
+    if (resp.fs.content_length == 0) {
+      auto cl = resp.fs.header(http2::HD_CONTENT_LENGTH);
+      assert(cl);
+      http2::erase_header(cl);
+    }
+  } else if (resp.http_status / 100 == 1 ||
+             (resp.http_status == 200 && req.method == HTTP_CONNECT)) {
     if (resp.fs.header(http2::HD_CONTENT_LENGTH) ||
         resp.fs.header(http2::HD_TRANSFER_ENCODING)) {
       return -1;
     }
-  }
-
-  if (resp.fs.parse_content_length() != 0) {
+  } else if (resp.fs.parse_content_length() != 0) {
     downstream->set_response_state(Downstream::MSG_BAD_HEADER);
     return -1;
   }
diff --git a/src/shrpx_mruby_module_response.cc b/src/shrpx_mruby_module_response.cc
index 145def0e..7e263804 100644
--- a/src/shrpx_mruby_module_response.cc
+++ b/src/shrpx_mruby_module_response.cc
@@ -233,7 +233,7 @@ mrb_value response_return(mrb_state *mrb, mrb_value self) {
       (resp.http_status == 200 && req.method == HTTP_CONNECT)) {
     if (cl) {
       // Delete content-length here
-      cl->name = StringRef{};
+      http2::erase_header(cl);
     }
 
     resp.fs.content_length = -1;