diff --git a/src/http/modules/ngx_http_fastcgi_module.c b/src/http/modules/ngx_http_fastcgi_module.c
index 17b7e83..2d9a18f 100644
--- a/src/http/modules/ngx_http_fastcgi_module.c
+++ b/src/http/modules/ngx_http_fastcgi_module.c
@@ -2007,8 +2007,12 @@
                 hh = ngx_hash_find(&umcf->headers_in_hash, h->hash,
                                    h->lowcase_key, h->key.len);
 
-                if (hh && hh->handler(r, h, hh->offset) != NGX_OK) {
-                    return NGX_ERROR;
+                if (hh) {
+                    rc = hh->handler(r, h, hh->offset);
+
+                    if (rc != NGX_OK) {
+                        return rc;
+                    }
                 }
 
                 ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
index 864fc4f..a64658f 100644
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -1891,8 +1891,12 @@
                 hh = ngx_hash_find(&umcf->headers_in_hash, h->hash,
                                    h->lowcase_key, h->key.len);
 
-                if (hh && hh->handler(r, h, hh->offset) != NGX_OK) {
-                    return NGX_ERROR;
+                if (hh) {
+                    rc = hh->handler(r, h, hh->offset);
+
+                    if (rc != NGX_OK) {
+                        return rc;
+                    }
                 }
 
                 continue;
diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index 20b1109..e8df555 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -1930,8 +1930,12 @@
             hh = ngx_hash_find(&umcf->headers_in_hash, h->hash,
                                h->lowcase_key, h->key.len);
 
-            if (hh && hh->handler(r, h, hh->offset) != NGX_OK) {
-                return NGX_ERROR;
+            if (hh) {
+                rc = hh->handler(r, h, hh->offset);
+
+                if (rc != NGX_OK) {
+                    return rc;
+                }
             }
 
             ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
diff --git a/src/http/modules/ngx_http_scgi_module.c b/src/http/modules/ngx_http_scgi_module.c
index cc865fd..9fc18dc 100644
--- a/src/http/modules/ngx_http_scgi_module.c
+++ b/src/http/modules/ngx_http_scgi_module.c
@@ -1114,8 +1114,12 @@
             hh = ngx_hash_find(&umcf->headers_in_hash, h->hash,
                                h->lowcase_key, h->key.len);
 
-            if (hh && hh->handler(r, h, hh->offset) != NGX_OK) {
-                return NGX_ERROR;
+            if (hh) {
+                rc = hh->handler(r, h, hh->offset);
+
+                if (rc != NGX_OK) {
+                    return rc;
+                }
             }
 
             ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
diff --git a/src/http/modules/ngx_http_uwsgi_module.c b/src/http/modules/ngx_http_uwsgi_module.c
index a1a76f6..5078ef7 100644
--- a/src/http/modules/ngx_http_uwsgi_module.c
+++ b/src/http/modules/ngx_http_uwsgi_module.c
@@ -1340,8 +1340,12 @@
             hh = ngx_hash_find(&umcf->headers_in_hash, h->hash,
                                h->lowcase_key, h->key.len);
 
-            if (hh && hh->handler(r, h, hh->offset) != NGX_OK) {
-                return NGX_ERROR;
+            if (hh) {
+                rc = hh->handler(r, h, hh->offset);
+
+                if (rc != NGX_OK) {
+                    return rc;
+                }
             }
 
             ngx_log_debug2(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index a111de8..8cc4ea5 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -4633,10 +4633,34 @@
 
     u = r->upstream;
 
+    if (u->headers_in.content_length) {
+        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                      "upstream sent duplicate header line: \"%V: %V\", "
+                      "previous value: \"%V: %V\"",
+                      &h->key, &h->value,
+                      &u->headers_in.content_length->key,
+                      &u->headers_in.content_length->value);
+        return NGX_HTTP_UPSTREAM_INVALID_HEADER;
+    }
+
+    if (u->headers_in.transfer_encoding) {
+        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                      "upstream sent \"Content-Length\" and "
+                      "\"Transfer-Encoding\" headers at the same time");
+        return NGX_HTTP_UPSTREAM_INVALID_HEADER;
+    }
+
     h->next = NULL;
     u->headers_in.content_length = h;
     u->headers_in.content_length_n = ngx_atoof(h->value.data, h->value.len);
 
+    if (u->headers_in.content_length_n == NGX_ERROR) {
+        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                      "upstream sent invalid \"Content-Length\" header: "
+                      "\"%V: %V\"", &h->key, &h->value);
+        return NGX_HTTP_UPSTREAM_INVALID_HEADER;
+    }
+
     return NGX_OK;
 }
 
@@ -5021,14 +5045,37 @@
     ngx_http_upstream_t  *u;
 
     u = r->upstream;
+
+    if (u->headers_in.transfer_encoding) {
+        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                      "upstream sent duplicate header line: \"%V: %V\", "
+                      "previous value: \"%V: %V\"",
+                      &h->key, &h->value,
+                      &u->headers_in.transfer_encoding->key,
+                      &u->headers_in.transfer_encoding->value);
+        return NGX_HTTP_UPSTREAM_INVALID_HEADER;
+    }
+
+    if (u->headers_in.content_length) {
+        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                      "upstream sent \"Content-Length\" and "
+                      "\"Transfer-Encoding\" headers at the same time");
+        return NGX_HTTP_UPSTREAM_INVALID_HEADER;
+    }
+
     u->headers_in.transfer_encoding = h;
     h->next = NULL;
 
-    if (ngx_strlcasestrn(h->value.data, h->value.data + h->value.len,
-                         (u_char *) "chunked", 7 - 1)
-        != NULL)
+    if (h->value.len == 7
+        && ngx_strncasecmp(h->value.data, (u_char *) "chunked", 7) == 0)
     {
         u->headers_in.chunked = 1;
+
+    } else {
+        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                      "upstream sent unknown \"Transfer-Encoding\": \"%V\"",
+                      &h->value);
+        return NGX_HTTP_UPSTREAM_INVALID_HEADER;
     }
 
     return NGX_OK;