The syntax highlight extension "SyntaxHighlight_GeSHi" is already pre-installed in the macOS MediaWiki App (I use Bitnami). This is great. I changed my "LocalSettings.php" file and added the line wfLoadExtension( 'SyntaxHighlight_GeSHi' ); After a restart of the services it works only partly. This means for example <syntaxhighlight lang="xml" line="1" style="border:3px dashed blue"> <dict> <key>Label</key> </dict> </syntaxhighlight> Shows the gray area and a dashed blue border. It does not colorize the code. Any clue what's wrong? What did I miss?