diff --git a/tools/sandcastle/.gitignore b/tools/sandcastle/.gitignore
index d53d9ae3..8e4fd3b4 100644
--- a/tools/sandcastle/.gitignore
+++ b/tools/sandcastle/.gitignore
@@ -1,3 +1,4 @@
 .ghc.environment.*
 dist
+dist-newstyle
 test/output/
diff --git a/tools/sandcastle/lib/Sandcastle.hs b/tools/sandcastle/lib/Sandcastle.hs
index 1eff4cdc..acdbb4a9 100644
--- a/tools/sandcastle/lib/Sandcastle.hs
+++ b/tools/sandcastle/lib/Sandcastle.hs
@@ -88,6 +88,7 @@ writePandoc fmt pdoc = case lookup (formatPandoc fmt) writers of
              & enableExtension Ext_pipe_tables
              & enableExtension Ext_markdown_in_html_blocks
              & enableExtension Ext_backtick_code_blocks
+             & enableExtension Ext_fenced_code_attributes
 
 formatPandoc :: Format -> Text
 formatPandoc = \case