diff --git a/doc/configuration.txt b/doc/configuration.txt
index 0c23dd1..ec89073 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -753,6 +753,10 @@
 * HAPROXY_MASTER_CLI: In master-worker mode, listeners addresses of the master
   CLI, separated by semicolons.
 
+* HAPROXY_STARTUP_VERSION: contains the version used to start, in master-worker
+  mode this is the version which was used to start the master, even after
+  updating the binary and reloading.
+
 In addition, some pseudo-variables are internally resolved and may be used as
 regular variables. Pseudo-variables always start with a dot ('.'), and are the
 only ones where the dot is permitted. The current list of pseudo-variables is: