diff --git a/requirements.txt b/requirements.txt
index 78ab336..3f9a173 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -33,7 +33,7 @@ typing-extensions==4.12.2
 
 # sphinx-immaterial[keys] https://pypi.org/project/sphinx-immaterial/
 markdown==3.7
-pymdown-extensions==10.16.1
+pymdown-extensions==10.21.3
 pyyaml==6.0.2
 
 # https://pypi.org/project/ipython/