diff --git a/doc/configuration.txt b/doc/configuration.txt
index b24c61b..ee93b39 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -14336,6 +14336,13 @@
   seconds, which means that you can't cache an object more than 60 seconds by
   default.
 
+process-vary <0 or 1>
+  Disable or enable the processing of the Vary header. When disabled, a response
+  containing such a header will never be cached. When enabled, we need to calculate
+  a preliminary hash for a subset of request headers on all the incoming requests
+  (which might come with a cpu cost) which will be used to build a secondary key
+  for a given request (see RFC 7234#4.1). The default value is 0 (disabled).
+
 
 6.2.2. Proxy section
 ---------------------