diff --git a/lib/Constants.php b/lib/Constants.php
index 68e54f78..7772ee38 100644
--- a/lib/Constants.php
+++ b/lib/Constants.php
@@ -35,4 +35,6 @@ const EBOOKS_DIST_PATH =		SITE_ROOT . '/web/www/ebooks/';
 
 const GITHUB_SECRET_FILE_PATH =		SITE_ROOT . '/config/secrets/se-vcs-bot@github.com'; // Set in the GitHub organization global webhook settings.
 const GITHUB_WEBHOOK_LOG_FILE_PATH =	'/var/log/local/webhooks-github.log'; // Must be writable by `www-data` Unix user.
-const GITHUB_IGNORED_REPOS =		['tools', 'manual', 'web']; // If we get GitHub push requests featuring these repos, silently ignore instead of returning an error.
+
+// If we get GitHub push requests featuring these repos, silently ignore instead of returning an error.
+const GITHUB_IGNORED_REPOS =		['tools', 'manual', 'web', 'ludwig-wittgenstein_tractatus-logico-philosophicus_c-k-ogden']; // Ignore Tractatus due to a FF70+ bug that causes MathML rendering to hang during build.