diff --git a/setupbase.py b/setupbase.py
index fbc00041d..acd593f37 100644
--- a/setupbase.py
+++ b/setupbase.py
@@ -151,6 +151,7 @@ def find_package_data():
         mj('MathJax.js'),
         mj('config', 'TeX-AMS_HTML-full.js'),
         mj('config', 'Safe.js'),
+        mj('extensions', 'Safe.js'),
         mj('jax', 'output', 'HTML-CSS', '*.js'),
     ])
     for tree in [