diff --git a/opensem/README.org b/opensem/README.org
index a4032f6..abb040c 100644
--- a/opensem/README.org
+++ b/opensem/README.org
@@ -37,7 +37,7 @@ opensem:
     paybox-system:
       paybox:
         test: true
-        rank: "001"  ## keep the double-quotes !
+        rank: 1  ## no need for zeroes before !
         site: 2XXXX9
         id: 2XXXXX4
         hmac-key: "FFAXXXXX...XXXXX"
diff --git a/opensem/hooks/paybox_system-relation-joined b/opensem/hooks/paybox_system-relation-joined
index 81b9b67..9db997b 100755
--- a/opensem/hooks/paybox_system-relation-joined
+++ b/opensem/hooks/paybox_system-relation-joined
@@ -22,6 +22,8 @@ hmac_key=$(relation-get hmac-key) || {
     exit 1
 }
 
+rank=$(printf "%03d" "$rank")
+
 [ -n "$test" ] && opensem:config-set PAYBOX_TEST "$test"
 opensem:config-set PAYBOX_SITE "$site"
 opensem:config-set PAYBOX_RANK "$rank"