diff --git a/pandoc-filters/titlecase_titles.lua b/pandoc-filters/titlecase_titles.lua
index 829202a5..82f4f334 100644
--- a/pandoc-filters/titlecase_titles.lua
+++ b/pandoc-filters/titlecase_titles.lua
@@ -2,13 +2,15 @@
 
 local decasify = require("decasify")
 local locale = os.getenv("LANGUAGE") or "en"
+local style = os.getenv("STYLEGUIDE") or "gruber"
 
 Pandoc = function (doc)
-  local language = pandoc.utils.stringify(doc.meta.language or locale)
+  locale = pandoc.utils.stringify(doc.meta.language or locale)
+  style = pandoc.utils.stringify(doc.meta.styleguide or style)
   return doc:walk {
     Header = function (element)
       local title = pandoc.utils.stringify(element.content)
-      local cased = decasify.titlecase(title, language)
+      local cased = decasify.titlecase(title, locale, style)
       element.content = cased
       return element
     end