diff --git a/docs/conf.py b/docs/conf.py
index 266cde1bb98..7f01e84460e 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -56,6 +56,7 @@
     r"https://cernvm.cern.ch/.*",
     r"https://tavianator.com/.*",
     r"http://eigen.tuxfamily.org.*",
+    r"https://pythia.org.*",
 ]
 
 # -- Options for HTML output --------------------------------------------------