add markup.highlight.noClasses: false

config.yml

@@ -198,13 +198,13 @@ markup:
     goldmark:
         renderer:
             unsafe: true
-#     highlight:
-#         # anchorLineNos: true
-#         codeFences: true
-#         guessSyntax: true
-#         lineNos: true
-#         # noClasses: false
-#         style: monokai
+    highlight:
+        noClasses: false
+        # anchorLineNos: true
+        # codeFences: true
+        # guessSyntax: true
+        # lineNos: true
+        # style: monokai
 
 privacy:
     vimeo: