diff --git a/doc/lua-api/index.rst b/doc/lua-api/index.rst
index e8d494b02..250227de3 100644
--- a/doc/lua-api/index.rst
+++ b/doc/lua-api/index.rst
@@ -893,7 +893,9 @@ Core class
 
   **context**: init, task, action
 
-  This function returns a new object of a *httpclient* class.
+  This function returns a new object of a *httpclient* class. An *httpclient*
+  object must be used to process one and only one request. It must never be
+  reused to process several requests.
 
   :returns: A :ref:`httpclient_class` object.
 
@@ -2581,7 +2583,9 @@ HTTPClient class
 .. js:class:: HTTPClient
 
    The httpclient class allows issue of outbound HTTP requests through a simple
-   API without the knowledge of HAProxy internals.
+   API without the knowledge of HAProxy internals. Any instance must be used to
+   process one and only one request. It must never be reused to process several
+   requests.
 
 .. js:function:: HTTPClient.get(httpclient, request)
 .. js:function:: HTTPClient.head(httpclient, request)