diff --git a/src/Text/Pandoc/Options.hs b/src/Text/Pandoc/Options.hs
index 6a3028b14..92ffee84a 100644
--- a/src/Text/Pandoc/Options.hs
+++ b/src/Text/Pandoc/Options.hs
@@ -369,7 +369,7 @@ defaultMathJaxURL :: Text
 defaultMathJaxURL = "https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml-full.js"
 
 defaultKaTeXURL :: Text
-defaultKaTeXURL = "https://cdnjs.cloudflare.com/ajax/libs/KaTeX/0.11.1/"
+defaultKaTeXURL = "https://cdn.jsdelivr.net/npm/katex@0.15.1/dist/"
 
 -- Update documentation in doc/filters.md if this is changed.
 $(deriveJSON defaultOptions{ fieldLabelModifier =
diff --git a/src/Text/Pandoc/Writers/HTML.hs b/src/Text/Pandoc/Writers/HTML.hs
index 8c5548196..63ce80ba9 100644
--- a/src/Text/Pandoc/Writers/HTML.hs
+++ b/src/Text/Pandoc/Writers/HTML.hs
@@ -300,6 +300,7 @@ pandocToHtml opts (Pandoc meta blocks) = do
                             _ -> mempty
         KaTeX url -> do
           H.script !
+            A.defer mempty !
             A.src (toValue $ url <> "katex.min.js") $ mempty
           nl
           let katexFlushLeft =