diff --git a/doc/airline.txt b/doc/airline.txt
index 0d269b4..974f53e 100644
--- a/doc/airline.txt
+++ b/doc/airline.txt
@@ -489,7 +489,11 @@ exposed.
   endfunction
   let g:airline#extensions#tabline#formatter = 'foo'
 <
-  Note: the following variables are only used by the 'default' formatter.
+
+  Note: the following variables are only used by the 'default' formatter. 
+  When no disambiguation is needed, both 'unique_tail_improved' and 
+  'unique_tail' delegate formatting to 'default', so these variables also
+  control rendering of unique filenames when using these formatters.
 
     * configure whether buffer numbers should be shown. >
       let g:airline#extensions#tabline#buffer_nr_show = 0