diff --git a/docs/server_manual/services/wms.rst b/docs/server_manual/services/wms.rst
index 0baadab3520..b6d36d2c7ce 100644
--- a/docs/server_manual/services/wms.rst
+++ b/docs/server_manual/services/wms.rst
@@ -1546,7 +1546,7 @@ URL example with the corresponding JSON output:
   REQUEST=GetLegendGraphic&
   LAYERS=airports&
   FORMAT=application/json&
-  SHOWRULEDETAILS=YES
+  SHOWRULEDETAILS=TRUE
 
 And the corresponding JSON output: