1 files changed, 4 insertions, 1 deletions
diff --git a/doc/lua-filters.md b/doc/lua-filters.md
index a5c9905ab..35610cea3 100644
--- a/doc/lua-filters.md
+++ b/doc/lua-filters.md
@@ -344,11 +344,14 @@ inside headers), removes footnotes, and replaces links
 with regular text.
 
 ``` lua
+-- we use preloaded text to get a UTF-8 aware 'upper' function
+local text = require('text')
+
 function Header(el)
     if el.level == 1 then
       return pandoc.walk_block(el, {
         Str = function(el)
-            return pandoc.Str(el.text:upper())
+            return pandoc.Str(text.upper(el.text))
         end })
     end
 end