diff --git a/fluid/README_fl.txt b/fluid/README_fl.txt
index 12480b039..056ddeb51 100644
--- a/fluid/README_fl.txt
+++ b/fluid/README_fl.txt
@@ -418,7 +418,9 @@ Type "data" <word> : C++ variable name
 
 Type "declblock" <word> : C++ code
 
-  none or "public" or "protected" : defaults to private
+  none or "public" or "protected" : defaults to private (obsolete)
+  "map" <word> : integer value, default is 2 (CODE_IN_SOURCE),
+      see Fl_DeclBlock_Type::write_map_
   "after" <word> : C++ code or comment following the block
   ... : inherits more from Fl_Type