diff --git a/book/external/sphinx-iframes b/book/external/sphinx-iframes
index 062c54a..e21273d 160000
--- a/book/external/sphinx-iframes
+++ b/book/external/sphinx-iframes
@@ -1 +1 @@
-Subproject commit 062c54a679c6dd44b948549498e755c7c5df1d73
+Subproject commit e21273da134cbf4753da5faf9adc277b8f1c3a1c