diff --git a/requirements-docs.txt b/requirements-docs.txt
index 308d2b0..221708f 100644
--- a/requirements-docs.txt
+++ b/requirements-docs.txt
@@ -8,7 +8,8 @@ alabaster==0.7.16; python_version<'3.10'
 alabaster==1.0.0; python_version>='3.10'
 babel==2.17.0
 imagesize==1.4.1
-mdit-py-plugins==0.5.0
+mdit-py-plugins==0.4.2; python_version=='3.9'
+mdit-py-plugins==0.5.0; python_version>='3.10'
 myst-parser==3.0.1; python_version<'3.10'
 myst-parser==4.0.1; python_version>='3.10'
 roman-numerals-py==3.1.0
diff --git a/script/update-requirements b/script/update-requirements
index f00a9d6..da96daf 100755
--- a/script/update-requirements
+++ b/script/update-requirements
@@ -60,6 +60,10 @@ versions['Sphinx'] = (
     "8.1.3; python_version=='3.10'",
     f"{versions['Sphinx'][0]}; python_version>='3.11'",
 )
+versions['mdit-py-plugins'] = (
+    "0.4.2; python_version=='3.9'",
+    f"{versions['mdit-py-plugins'][0]}; python_version>='3.10'",
+)
 
 
 def write_packages(fh, packages, header, prefix=''):